Engine Log
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Log of the engine teardown and rebuild for Blue Lite

September 7, 2002, Blue 2164 Mi.

It's Saturday, and one more long ride will put over 1000 miles on Blue Lite, my 1970 Honda CD175 "parts bike".  The weather is warm and sunny so I headed for Grand Bend, Ontario, a summer beach town on Lake Huron.  The odometer was reading 2164 miles.

After an hour of 60 mph cruising, I arrived at  Grand Bend and I could tell something was wrong. The engine idled roughly when I restarted it after parking at the beach for 10 minutes.  I thought I heard more rattling noise than usual on the run out there, but it's hard to tell.  Anyhow while scooting slowly in town I heard a bang then silence and Blue coasted to a stop. Everything looked OK so I took off the points cover, spun the starter but the points cam did not move.  Also it kicked through more easily than usual.  I guessed it was a broken timing chain and pushed the bike to a pay phone and called for the "Knight in Shining Armour" as she likes to call herself, Mary Ann.  Luckily she was able to move my BMW K1100LT out of the garage on her own because it was blocking access to my bike trailer. She met me a couple of hours later in Grand Bend with the car and trailer. This was the first time I have had to use the rescue trailer to bring home a stranded bike.  

While loading Blue I could see that by compressing the forks, oil was leaking out of the left fork drain plug. The rubber washer I put on the drain hole has cracked.

I am going to put Blue in storage with 2241 on the odometer (less than 1000 miles since I got it).   I have drained the carburetor and emptied the tank.  I put some two stroke oil in the tank to absorb the last bit of gas and shook the tank to coat the inside for rust prevention.   

At home I looked up CD175 cam chain problems on the Used Bike Guide on the internet.  There were two reports of cam chain snapping, and both times the valves and pistons suffered, and the engine needed to be replaced.  Not good news for Blue, but I will take off the top and have a look.  I  was thinking there is a chance that Blue's valves were untouched, because the cam shaft has a slight preference to stop at a point where all the valves are retracted safely.

September 8, 2002, Blue 2241 Mi.

Click firstlook.JPG (54428 bytes) on the thumbnail on the left for a bigger picture of what I saw when I took off the top engine cover.  The cam chain had come apart at the clip link. I found bits of aluminum when I drained the oil. The cam chain is still partly wrapped around the cam shaft sprocket with the master link sticking up.  The clip and sideplate are missing.  The master link's pins are bent apart.

The cam chain tension mechanism seems to be working because when I loosened the adjusting bolt, something made a springing sound inside the engine. I just found a posting on usenet that says another indication of cam chain rattle is engine surging at idle, which Blue has done since I first fired her up 1000 miles ago.

Posted on rec.motorcycles.tech by Andy Watson on 2000/04/02

It is unlikely that the rattle you are getting is due to the valves as this should be constant at all rpm's. Its more than likely (in my opinion) to be cam chain rattle at idle, especially if your engine is varying in idle speed (surging a bit). Should disappear if you hold the throttle constant at about 5k/rpm or some such higher speed (i. e. put constant tension on the cam chain).

If that is true then I had lots of warning that the cam chain was slack, because I had the surging that is pretty easy to detect (mirrors start shaking then smooth out again about every 3 seconds while idling), and I did also hear what sounded like a cam chain rattle.  But I was unable to stop the rattling using the cam chain adjustment bolt.  And it's too big a job to get the engine out just to see if there is  a problem.

I measured the length of the cam chain without the master link. It is 63.7 cm. to 63.3  cm., depending on if I pull it out tight or compress it a bit.  That does not seem like a lot of wear on the chain.  Also, there was about 8 cm of lateral bend in the chain including the width of the chain. I measured 8 cm from the middle of the arc to a line between the two ends. The cam chain has 82 links (including the master) and the bent master link has DK219H written on it.  According to the parts manual for the K4 model (actually I have a K3), the chain is DID 219H-82L.

October 16, 2002

I received the new cam chain for Blue Lite.  It is a Daido DID 219T, not 219H.  It seems the only difference is that this chain is endless.  There was no master link in the box, and since it is 106 links and not 82 that I need, I will need to remove some links and install a master link.  The new chain has a little less side play than the old one, and only about 1.5 mm shorter, so I think that the original chain was not badly worn. I ordered the link from Daido for their chain.  Apparently master links are not swappable from one manufacturer to another even for the same size chain.  The new chain cost $45.99 including tax from Zdeno's.  There was no rivet link with it. The link should take a few more days to order.

October 17, 2002,  Red 7760 mi.

I got the rivet link today for the cam chain for about $3.25 including tax. With grinding and a punch, I took out a 24 link section from the new endless chain and I can now use the rivet link to join the rest when I'm ready.  I measured the diameter of the pins from the two chains.  The old DK219H has a pin diameter of 3.01 mm.  The new Daido 219T and the rivet link both measure 3.14 mm diameter.  The rivet type link is supposed to be better than a clip type, but you can't take the rivet link apart if you make a mistake. (Prediction: I will make a mistake.

December 5, 2002

Removing the Engine

frame1.JPG (42846 bytes)  It took one afternoon to get the engine out. Most steps are pretty obvious after reading the manual.  I thought it would be best to unbolt the horn because it looked like it was in the way.  I left the brake pedal in place, even though it gets in the way because it is a bit of a pain to remove with my center stand shaft being backwards.  The engine was light enough for me to get out by myself and carry into the house and downstairs.  Apparently I looked a bit out of breath afterwards, because Mary Ann was staggering around the house breathing heavily for a while pretending to be just as pooped as I was even though she only held open the door.

engine1.JPG (50892 bytes)With the engine out, I can see there is a lot of rust on the frame inside the engine hangers near the swing arm. (visible in the photo of the bike frame). Also I have one connector to the generator that I can't remember which wire it runs to.  And the electric starter cable was difficult to get out from behind the starter motor.  The chain will not come off the front sprocket because of lack of clearance, I had to undo the master link and run it around (not a big deal, really).

Removing the Head

When I tried to pull the cylinder head off, a couple of the studs got stuck inside the holes and it jammed about 2 inches up. I could not get it off, so I asked for help on the internet.  I received this advice via email:

This is caused by the pivot shafts of the tappet arms as they can move inwards (towards the cam chain tunnel) along their tracks and rub up against the unthreaded portion of the studs so that when you pull up the cylinder head the threads of the stud stop against these pivot shafts.


Remove the four screws on the RH side of the cylinder head and remove the side cover to expose the pivot shafts. Place a loose bolt inside the hollow of the pivot shafts and pull outwards towards you. If you pull all the way the tappet will fall down so you only need pull about 5mm. Remove the points cover on the other side of the head, remove the points base plate and remove the auto advance mechanism. Remove the four screws holding the points housing to the head and withdraw it. Same procedure as above i.e. using a bolt or screwdriver withdraw the pivot shafts approx 5mm.

December 6, 2002

I finished removing the cylinder head and block today, using the method above.  Actually I only needed to remove the points housing, then loosen one jammed rocker pivot pin.  After that the head and block lifted off easily.  Oil has escaped from the cylinder base and near  the head gasket as well. That could be the O-rings or the gasket. In either case I have a new set ready to go in.

Broken Timing Chain

It looks like snapping the cam chain did no damage to the engine at all.  By luck, all four valves are closed, and have not moved since the cam chain snapped.  The cam chain runs in a cavity that is partly separated from the gearbox and crankshaft by walls.  All the broken bits should be confined to this area, I hope.   I found the missing master link side tensioner.JPG (62918 bytes) plate from the broken cam chain in the bottom of the cavity.  The biggest part of the broken clip came out with the oil drain. I also found the fragment of the clip that broke off right beside the master link plate.


Why would the cam chain get loose and break if the tensioner was working?

  1. Maybe I did not have the correct adjustment instructions.  The CD175 owners manual says to adjust while at the engine is at TDC, I didn't have the correct manual and adjusted while it was idling.

  2. When adjusting the tensioner, I think you need to be careful to tighten the adjusting bolt enough to stop the tensioner rod from sliding upward while riding.   

  3. If you ever turn the engine backward, you might put stress on the normally slack run of the cam chain where the tension sprocket is.  That can happen if you are turning the engine using the rotor bolt, as when doing valve adjustments. 

  4. Maybe the problem occurs because the chain is a bit worn. However, Honda says that the cam chain wear is not a problem in the normal life span of an engine because it is running in a clean well lubricated environment.

  5. The master link clip could have been installed backwards. In the official K4 parts diagram,  the master link clip is shown facing the wrong way. The K1 - K3 manual has it going the right way, and the Haynes manual has a photo of the clip the right way and a parts diagram showing the wrong way also. 

There are grooves where the cam chain was rubbing on parts of the head and part of the cam chain tension block, so I guess the chain was not tight enough at least on this bike. I could not stop the cam chain noise by adjusting the tensioner  last summer.

Honda's Upgrade to the Timing Chain Tensioner

Note from the future: I will find out in February that Honda made one (and only one) change to the tensioner, to  increase the adjuster bolt size on the K4 model. They must think the  problem with timing chain tension is due to the adjuster bolt not being tight enough.   Or that the small adjust bolt stripped too easily.

December 7, 2002

Pistons and Rings

I removed the top two rings on the left piston.  I looked at my new piston to compare it with the old.   The box it comes in says part # 13011-313-010 STD,  which is the standard size according to the K4 parts book.  The box has RINGS ARE .25 OVER pencilled in.  "ART" and "313" are embossed on each side of the new piston, and "Honda" and "302"are embossed on the old piston.  My good metric calipers are too small to show piston size, but with my old vernier calipers I can tell both new and old pistons are the same diameter front to back.  "25" is stamped on the top of all the rings near the gap.

The new piston rings I bought are 3022-235-000, which are the same as a set I just saw on eBay also marked as .25 mm oversize.  The part number is not the same as the K4 book, but it could be one size over for an earlier 175 twin.  To size the ring, it should be placed square in the bore about .6 inches from the bottom of the cylinder, and the gap measured.  Over .032 inches gap is too much.  If the gap is too small (less then .006"), the end of the ring can be ground to make the gap bigger. The new oil rings can't even fit in my cylinder, so they will need grinding for sure.  One of the  the new compression rings is .012" but the rest need grinding to make them fit this cylinder. The gaps are .020 and .025 for the two old top rings from the left piston. 

My new piston kit includes a set of standard size pistons, but the rings are one size over. I will not have to bore out the barrel to fit either the new rings or pistons.  The pistons can go right in with no changes. The rings need the gap ground to .006" first. Apparently rings are hardened and an ordinary file will not work, you need a grinding disk.

I found a website that has some pictures, mostly two stroke piston fitting. Click here [EXTERNAL] for Dan's motorcycle course pistons. Lucky my piston does not look like that.

December 9, 2002

Points Housing Oil Leak

One problem I have known about since last summer is an oil leak around the breaker points housing.  I now have the points housing off, I have the new gasket and cam shaft bearing oil seal, so it's a good time to fix the leak.  Getting the old oil seal out was the usual procedure: 1. Begin by destroying the old seal 2. Check if I really have the new seal.  3. Get out a hammer and almost wreck the points housing. 4. Check the internet for ideas. 5. Read the manual. 6. read the Haynes manual. 7. Think. 8. Get out the propane torch, gloves, and pliers. 9. Heat the points housing gently all over. 10. Pop the seal out easy as pie with a screwdriver.  11. Hammer in the new one before the housing cools off.  (Note: It's best to use a socket to drive in the oil seal, to avoid distorting the seal by hitting one side at a time)

Now it seems the points housing will not go back on easily, because one pivot shaft does not slide completely into the hole in the housing. The rocker pivot shaft is not securely held in place at the pointsfar.JPG (24356 bytes) inside end, and it is possible for it to get pushed too far and interfere with the stud. At the outside end of the pivot shaft, it fits in to a hole in the points cover housing, and also helps locate the housing (and the cam bearing) accurately.  The reason I could not remove the cylinders until I took off the points housing was because the shaft was pushed in against the stud.  As you tighten the housing against the cylinder head, the pivot shaft pushes into the stud's hole  and prevents the removal or installation of the cylinder block.

I was also looking for a valve spring compressor.  Out of about 10 I have seen already in the store or on eBay, only one might work.  The problem with using a normal compressor on the CD175 is that the compressor usually can't fit through the screw-on valve adjustment cap.  Most typical engines valves are more accessible than the Honda when the valve cover is off.

I bought another cam chain rivet link to replace the one I lost.  They say that when you lose something, as soon as you buy a new one, the missing one turns up.  The missing link fell into my hand about 8 seconds after I tried to put the old one away in a safe place, maybe a new record.

December 10, 2002

I removed both pistons, the wrist pins were not stuck, and I could push them out with a screwdriver.

I checked the cam chain tensioner again, and I see there was some damage to the rubber at the end of the tensioner spring, where the loose chain has worn grooves into the metal housing.  The rubber fell off the end of the tensioner rod.  In the parts manual, these are shown as two separate parts, so I just crimped the rubber back in with vise grip pliers.  

I was reading about gaskets, apparently they swell when in contact with oil, and you should keep them clean and dry until ready for use.  I didn't know, and some of my new gaskets already have oil on them.  I tried to clean it off with "Simple Green" and hopefully they'll be OK by the time I need to use them.

1. vlaveclamp.jpg (83282 bytes)      2. springcompressor.jpg (59520 bytes)     3. keepers.jpg (63434 bytes)

I could not find  a valve spring compressor to fit the the Honda's valve inspection opening.  I visited four places, including a couple of specialty auto tool places. My genius friend Barry, said there was no problem making a machined piece that would press down the valve.  

Click on the pictures to see close ups of the home made valve spring compressor in action. It is a cylinder shape cut open on one side for  accessing the collars. Note the machined groove around the bottom of the compressor that exactly fits the round valve spring retainer to make it more secure. I put on my  blue and yellow clamp to complete the compressor assembly.  A 6" C clamp would be better and cheaper.  I used another clamp to hold the the head down on the workbench before I started.

Pc130002.jpg (111914 bytes)And there is one more picture to show, this is Barry's lathe.  I think this is the actual machine that he used to make the so-called home made valve spring compressor.


December 14, 2002

I got a rotary hand held grinding tool yesterday like a Dremel.  With the valves out, it was possible to clean them up.  

ccbefore.JPG (64500 bytes)A few days ago I had started cleaning the valves and combustion chambers before I took out the valves.  You can see the grooves that were chainsawed into the head by the cam chain in the upper middle of the picture.


IM001075.JPG (22408 bytes)This is a picture of  the tops of the valves after cleaning. Some of the sandpaper disks removed too much metal, some were OK.  Apparently some valves may have a thin hard surface coating that you are not supposed to remove.  In this case, it looked like there was already some pitting on the valves.

IM001076.JPG (44876 bytes)Here are the valves in the cleaned combustion chamber. There is a "3" stamped on the face of the exhaust valve that I can see now.  The cleaning should reduce the compression ratio a bit.  Last winter, the compression tested higher than specifications.


December 18, 2002

I had a hard time removing the oil control ring with my fingers, so I bought a pair of 'piston ring pliers' from the local auto parts store for $10.  With these pliers it took me only a few seconds to break my oil control ring. Good thing I have a spare set. These pliers are Lisle tools #33500.  They are called "Piston Ring Installer" and are stated to install and safely remove piston rings from 3/64 to 1/4".  I was using them to remove the oil control ring which is about 5/64".  The main problem is that they do not hold the ends of the piston ring securely, and the gap on the little piston rings is too small for them to fit into.  I tried spreading the ring by hand just to fit the pliers in. Second problem is the ring does not stick out far enough to get into the pliers. And third, the rings are too weak to resist breakage when you do get hold of them.  I imagine a large automobile piston ring might be more compatible with these pliers, but the tiny Honda rings will not tolerate being stretched very far.

I had to use my Dremel tool and cutting wheel attachment to grind off the ends of my oversized spare rings to use them as replacements in my standard size cylinder. All the rings need at least .006 inch end gap.  The whole job was not too long.  It's about one second to shave .001" off the end of the ring, but I took  a lot of time measuring the ring gap in the cylinder bore as I worked, which also helped keep the rings cool enough to hold.

December 28, 2002

Cylinder Base Gasket was stuck to the bottom of the cylinder block, and took me about 3 days to remove, a total of about 4 hours of scraping, chipping, slicing, and scratching. 

The only tool I find really helpful in removing gaskets is the razor blade window scraper.  I tried spray-on gasket remover, and I can't tell if it helps or not.  Same with a propane torch.  I used a small scraper from a wood carving set, and a razor blade window scraper that I got at a hardware store.  It is important to not remove any aluminum from the surface under the gasket. I did scratch the aluminum a little. I am not an expert at this, but I learned some techniques as I went along.  One trick was to use a knife hone to sharpen the edge of the window scraper blade from time to time.  I think it helped.  New blades also work very well.

I also used Scotchbrite cloth to clean up the gasket mating surface, then found out that someone on the internet says that Scotchbrite is no good because it removes too much metal.  Well as usual, I do something first and worry about it later.

December 31, 2002

Another trip to the auto parts store (Canadian Tire) netted a can of foaming engine cleaner.  It is made of xylene and mineral spirits.  It smells too bad to use carelessly indoors.  It also is not very effective considering the smell.  Lucky it was above freezing today, so I did some spraying outside.  I sprayed the cylinder block and head with this stuff, and then used Scotchbrite pads to clean between the fins. The engine is gradually getting cleaner, but it's a lot of work.  The benefit from working so long to get it clean is that I have a chance to look at the engine carefully to see any problems with it.  Cleaning is probably taking more time than anything else except shopping trips for parts and tools.

Valve Lapping

I was not able to find a one inch suction cup on a stick to twirl the valves for lapping. Some were available smaller and larger. I will try twisting the valve using a screwdriver in the slot in the valve face.  But I still need to find some fine grinding compound, or maybe use some rubbing compound.

January 02, 2003

A trip to another automotive store got me a jar of Permatex "Valve Grinding Compound" No.474G  for about $11 for a 115 ml jar.  (I assume it will last 200 lifetimes.)  It has caution of harmful vapour, unfortunately "use under well ventilated conditions".  I hope I don't get too sick..  I have no idea why the warning is there, it does not smell bad, and  its supposed to be grit mixed with grease.  Further warnings are that it is supposed to be used for "Hardened steel seats or cast blocks."  The seat on the valve side might be hardened steel, and the other side may be cast aluminum, if that's what they mean.  When working on a motorcycle, I think you must not let yourself get too worried about warnings.  

I first cleaned out the valve guides with a wad of paper towel.  Then I inserted each valve in its original guide with the grinding compound and used a screwdriver to twist the valve back and forth.  There is a machined slot in each valve face, I don't know what for but it works for lapping.  I twisted back and forth about 20 degrees, then popped up the valve and turned it a bit then continued all around.  I finished off cleaning with a paper towel.  I will do a major soap and water cleaning before final reassembly.

I can see a fairly even dull gray finish on the seat all around, so I assume it is OK now.  I may check the leakage later when the valves are assembled with springs.

January 05, 2003

leftbefore.JPG (38866 bytes)Cylinder De-glazing

I didn't want to pay $35 for a cylinder de-glazer so I removed the glaze by hand with silicon carbide paper. I used a slightly coarser paper to start, and I finished it with #320. Click on the top thumbnail for a close up of the left cylinder before deglazing.  The next picture is the right cylinder after I had worked on it about half an hour. I tried to get a cross rightafter.JPG (40042 bytes)hatched look by rubbing diagonally.  It takes a lot longer than using the tool.  I did the de-glazing 25 years ago replacing the rings on my Yamaha 250, and I ran the bike a total of 50,000 miles without a problem.



January 06, 2003

Installing Piston Rings

I am starting the reassembly with the piston rings.  I already had the experience of breaking an oil ring on disassembly, so I need to be extra careful now. I did not use my special piston ring tool.  I put all the rings on from the top of the piston by hand, starting with the oil control ring.  It was pretty easy, actually. The rings all have the stamped number on top.  Two of the compression rings have 1N on the top, and two have just N.  I don't know what that means, so I made 1N my top ring, even though they all look the same. (NOTE: Later I will find a way to tell that 1N is actually the top ring, and that it is important to do it right.)  A few weeks ago, I made sure all the end gaps were OK by filing them with a Dremel tool.  And apparently, all new rings are made a bit oversize and you are expected to file them down.  I actually do not believe this myself, but it does make sense to check the gap before putting them in the cylinder.

Clean the Cylinder Head

I have a list of jobs to do to reassemble the engine.  The next one was to clean the cylinder head in soap and water.  I had a bit of trouble cleaning out the vertical oil passageways that run up the back two stud holes.  I tried to push a cloth through but it got jammed because its very rough inside.  Finally I used a coat hanger to pull a cloth wad through.  Finally I cleaned out and oiled the valve guides then I put the entire head in a plastic bag and put it to the side with the other bagged parts.

January 11, 2003

A Junk Bike for Parts

desertrat.JPG (18535 bytes)I picked up another CD175 that needed a home.  This time it's a red K4 with a stuck engine that I got Peterborough on Thursday from Tony Ton. This one is going to be known as Junk Bike. The thumbnail on the left shows the bike on the trailer, the engine, tank and seat in the back of the car.  There were lots of missing pieces, and the pistons were stuck.  The reason there were so many missing pieces is that the engine was IM001112.JPG (77506 bytes)removed to fix it, the job never got finished, and all the loose pieces were lost. Missing pieces include mufflers, engine hangers, swing arm pivot and brackets, horn, ignition switch, chain case, left side cover, and all sorts of screws and nuts.  Actually too many parts to list.  On the other hand, a lot of parts are there to share with Blue and Red.  Also both tires were flat, and the wheels do not spin freely. The bottom of the seat pan is pictured here, just because my camera takes excellent pictures of rust.. (click on the thumbnail for full effect)

My first objective is to free the pistons so that I can get the cylinders off  and use the cam chain tensioner for Blue, if it looks any better.  Then I will try to fix Junker's engine to get it running in Blue using the Blue's old cam chain.  I will likely need to hone the cylinders and I can reuse  Blue's old pistons. Getting Blue's gear shift lever onto Junk Bike's shaft was not easy so I got out a sharp needle file and cleaned up the splines.

IM001116.JPG (76211 bytes)The paint is severely weathered, but it does not look like much rust on the painted parts yet, and they are not dented.  The tank is all rusty inside with a spot of bad rust outside near the seat, and the seat's pan is rusted away to nothing around the edges.  I may be able to salvage a few parts from the seat, for example like the mounting brackets. which are not rusted through.


1 IM001110.JPG (72426 bytes)   2 rhpiston.JPG (143780 bytes)   3 IM001122.JPG (169271 bytes)   4 lhpiston.JPG (134706 bytes)

Removing Junk Bike's Cylinder Head

Each picture above is a thumbnail that you can click on for a larger view (if you have a strong stomach).  The digital camera is so sharp  you can see what Tony guessed were "dog hairs" in some of them. The master link could not be seen, so I tried grinding the pins out of the top link on the cam chain and punching them out, but gave up because it took too much force. Then I just cut the cam chain side plates with a Dremel cutting wheel. That worked. I used a rag to catch all the grinding bits, and that rag caught fire from the shower of sparks.  Good thing I was not using gasoline as a lubricant. I will be able to use the Junker's master link on Blue Lite's cam chain for a free complete cam chain.

The cam chain was tight, so I loosened the tensioner.  The bolt was much tighter than how I usually do it.  My new Year's resolution is to tighten the cam chain adjuster bolt much more than I did before when adjusting the cam chain on a CD175.  The adjuster lock nut was also much tighter than I do it.  But the CD175K4 has a 10mm lock nut which you can slip a socket over and put some real force on it.  The K3 bikes had an 8mm locknut.  Junk Bike has the same wear marks inside the engine where the loose cam chain at some time sawed into the casting, just like Blue Lite (and maybe Red too, for all I know).

The left piston (picture 2) looks the worst.  The crud on the pistons is pretty deep, and I have already soaked them in oil and WD40 in preparation for freeing them from the bores. 

It is now 6:00 PM, and I managed to get most of the crud off the top of the pistons and cylinder block.  It actually was not baked on hard and just wiped away with a plastic scraper and paper towels.  Then I decided to take off the rotor cover and see if the pistons were at top dead center by looking at the timing marks.  One rotor cover screw was stuck, and I am getting tired of wasting time on these stuck screws.  The rotor screws are difficult to find, and I don't like drilling them right away.  I can't get vise grips on these oval machine screw heads, so I went with code yellow. First I used a punch to reshape the previously buggered screw head so my #3 screwdriver is so tight I have to hammer it in and it can hold itself in place horizontally by the tip.  I put a T handle on the screwdriver.  I fired up the propane torch and heated the screw head.  Then I took a cloth with cold water and cooled the area around the screw. I put one hand to hold the other side of the engine and one hand to turn the T handle, I applied the most pressure I could and it popped loose. Code Yellow has worked quite a few times for me. Code Orange is to use a sharp chisel on the edge of the screw head.  Code red is to drill it out.

With the rotor off I could see it was about 10 degrees off TDC, so I turned the rotor using a socket wrench to top dead center, and doing so I could lift the cylinder block and pistons together about 3 mm off the engine case.

January 11, 2003

Piston to Cylinder Clearance

I spent some time tapping the piston and heating the cylinder.  I'm using a regular carpenter hammer and dropping it about half an inch by its own weight onto the piston crown.  I'm really just trying to help the oil penetrate with vibration, I don't want to break anything.  I notice the left piston has a deader sound than the right piston, and the hammer does not bounce as much, but no idea why.  I might think that a dead sound indicated things were moving just slightly, but it sure doesn't look like it.

Would it be better to let the engine sit outside at 0 degrees F?  Aluminum shrinks more than iron in cool temperatures. The coefficient of thermal expansion for aluminum is .0000128, and iron is .000006.  The difference will be about .000006.  A one degree. F drop on 1 inch radius will increase the clearance about .000006 inches, or .006 thou times 70 degrees = .42 thousandths of an inch. all around. Because that number is so small, I don't think freezing the engine is going to make a difference to the tightness of the piston in the bore, if both the piston and the cylinder are the same temperature.

I calculate that by heating the engine to 470 degrees I would lose about 3 thousandths of an inch (all around) which is makes the situation significantly worse. And if the engine was 470 deg. f and the piston was 0 deg. f, I would gain 3.3 thousandths all around, if I knew how to do that.

I used to think the reason for two cylinders on the 175 was to reduce vibration. While researching the thermal expansion, I realized that Honda made the 175 cc engine a twin because it reduces the clearance needed between the piston and the cylinder, and helps the piston last longer.  That is important especially in an air cooled engine that needs greater clearances to start with. And these small pistons seem to last forever in the single cylinder Honda 90.  But by using two cylinders on the CD175, there was more vibration than the 90, because both pistons move up and down together.

Pistons Start to Move!

I just found a website with a method that works for the pistons.

http://members.ispwest.com/barrymcp/CA77_Dream/CA77_project_log_1.html [EXTERNAL]


Barry's method is to use carb cleaner to soak the pistons, then use a breaker bar to turn the rotor nut.  Maybe it's obvious to some, but I will mention that I turned the nut clockwise.  I tried the other way, and the nut just unscrews.  The closer the rotor and crank is to the TOP indicator, the more leverage the crank has on the pistons.  Mine started off OK, the pistons moved about a quarter inch down because the crank was near the top to start with, but then the pistons soon jammed again as I got further down. I plan to keep slowly adding wood shims under the cylinder and turning until the thing is off.


There is another method using a grease gun and a sparkplug grease fitting to unstick the engine, which I didn't try.  I was afraid that putting all the force on one piston might break the crankshaft that connects to the other (also stuck) piston.  Maybe next time, if I ever buy another seized engine.

Seat and Gas Tank

I took some time to look at the seat and gas tank, because they are sitting around getting in my way.  The seat is so rusty every time I move it a pile of rust falls on the floor.  I think I can use part of the seat pan as the base for a solo seat and custom luggage rack.

A faded red US spec K3 sold on eBay for only $350 U.S. on Jan 3.  I missed it because it closed early with a "Buy it now". It looked like it might have been worth more.  Good condition exhaust pipes and mufflers installed new in '86, 4756 miles, with title, original toolkit and owners manual, full chain case. Faults are fading, a little surface rust, sacked out seat, stuck throttle cable, no battery, has not run for 10 years, but the motor turns over.  That is almost like showroom condition after working on Junk Bike's seat this morning.

January 13, 2003

Gas Tank

I took off the petcock, and found it was in quite good condition, considering how rusty the tank is.  Except for the main holding screw (I had to drill it), everything looked good, including the rubber rings and the four hole gasket.  The alloy body and sediment cup had no corrosion inside.  By comparison, Blue Lite had some serious pitting in the petcock body and cup.  What took the most time on Junk Bike was unplugging the reserve passageway, which had filled solid with hard crud.  I used a pin and some paper clip wire and finally broke through after 15 minutes of digging.

I emptied out the rust that was rattling around inside the tank. Then I tossed a handful of nuts and bolts into the tank and shook it around until I was tired (1 minute).  Some more rust came out, but more powdery than before. The inside of the tank appears just as it did when I started - rusty.  There is patch of rust on the outside of the tank where the seat was touching it. Unfortunately, there are some pinhole leaks in this area, which would need to be soldered or brazed.

Cylinder Head

I started taking apart the cylinder head.  Most screws are stuck or missing, but they can be destroyed and replaced by generic fasteners if I have to.  The screw-on valve inspection caps are not easily replaceable, but are also stuck, and the nuts are unfortunately buggered.  If they are stuck so tight that a 12 point, 19 mm socket will round off the nut, get them off by tapping with a chisel at the outside edge, where leverage is the maximum. I always thought that it was this issue of buggering up the inspection caps that inspired Robert Pirsig to write "Zen and the Art of Motorcycle Maintenance".  I screw those caps on very lightly with a wrench, and I never lost any.

I also removed the ignition advance mechanism, which seemed to be seized and I freed it up with some oil.  I can check the spring tension later.

January 17, 2003

More work with the stuck pistons.  I see that the right piston is more stuck than the left, because of the way the cylinder block is tilting.  I can get more wood shims under the left side, so I knocked the cylinder back straight again.  I took the whole engine outside to freeze for the night, and that should give me half a thousandth of an inch more clearance all around.

I found a set of sharp picks at a tool stall, and used them to clean out the spark plug threads in the engine.  It was amazing how much crud was in the grooves

Cylinder and Pistons are OFF

Finally got the pistons out.  Very labor intensive, moving the pistons 2 mm at a crack almost all the way out.  It was just as tight on the last millimeter as it was on the first. The right cylinder was the worst, tighter and harder to move and I saw it had a lot more rust and corrosion when I did get it out.  All the compression rings on both the pistons are stuck, too.

I can't explain every detail of the piston removal, but generally, I shimmed up the cylinder block with wood as high as I could with the crank at top dead center.  Then I turned the rotor nut clockwise until I heard the piston move (usually 2 mm at a time).  Often, one piston would move but not the other, so I alternated sides to keep the block level. When the crank was more than 10 degrees off center, I lost the massive leverage the rotor has, and it would not turn any more (or the nut would slip - can't explain why, but I don't think the rotor bolt was stripping).  Then I would turn it back to top and shim up the cylinder again and repeat the process.  I needed a lot of wood shims for this job, and some thicker pieces too.

I'm not sure how much good it was, I put the engine outside to freeze, then brought it inside hoping it would be easier to work on a very cold engine.  And when the piston was far enough out, I turned the engine upside down to spray WD40 on the lower half of the cylinder and let is sit for a while before continuing, but that was pretty near the end.

There is a lot of surface rust on the crankshaft.  The crank seems to move normally, so the bearings might be OK.  I would not normally expect rust inside the crank case, but Junk Bike's engine was missing all the head dome nuts, so maybe water got in under the loosened cylinder base gasket.  I checked inside the oil filler plug and I do not see any rust the gears.

Also, removed the pistons and the valves today.  One piston wrist pin was stuck on the connecting rod, so I pushed it out with the other pin and a huge Vise Grip (the welders clamp type)

January 19, 2003

Piston Rings Stuck

I got the oil ring off the left piston intact, and it has an acceptable end gap of 10 - 15 thousandths of an inch.  Both compression rings are still stuck, but I only needed one oil control ring to put on Blue Lite's old pistons to make a second complete set of pistons and rings.

On the right piston, I tried soaking overnight in carb cleaner, heating with a propane torch, boiling in water and vinegar for half an hour, and finally got the oil control ring a bit loose at the end, but broke it into three pieces before getting the middle part unstuck.  The top ring is also now broken in pieces, and one piece is still in the groove.

January 20, 2003

I got socket (hex key) screws for the engine side covers.  I found it difficult to find a place to sell the screws I wanted in the right pitch, length, style, and finish.  So I opted for plain finish (black) socket screws 50 mm long, fully threaded.  That way I can cut them to any length I want.  So I got a box of 50 for about $25.  I am going to try to re-use the original screws, but where I can't get them off with Vise Grips, I am going to drill them out and cut a socket screw to the right length to replace them.  Then next time it'll be easy getting the socket screw out with an Allen key.

Junk Bike's Front End

I took the front end off the Junk Bike and brought it inside, along with the rear fender.  So far the forks, front axle, and brake drum look pretty good.  Even though there is water inside the forks, the action is very smooth, and the fork tubes are free of nicks and scratches. Even the outside of the fork bottoms looks almost new under the dirt, especially the left one. I see almost no brake dust in the front hub, and rubbing with steel wool gives a shiny smooth braking surface. The brake shoes look like they were almost never used. It should be interesting to see if the back brake is the same.  I will be using this front end on Blue next summer.

Surprisingly, I found that the fading on the rear fender is actually a coat of dull silver that a PO has put over the bright candy red paint.  The fading on the front fender is real, though.

I am a bit puzzled about the condition of the components.  I don't understand how some parts can look so new while other look so worn out, beat up, or corroded.  One explanation might be that these parts were replaced recently, but I don't have a clue why.  Anyhow a great reason to buy a bike for parts is that you can be surprised by some items in really good condition hidden under the dirt.

I took apart the front brake because it was stiff, and greased the pivot and the cam surface, and I oiled the brake cable which was bent, rusted and stuck when it was on the bike, but now it seems to work fine.

January 22, 2003

Engine Rebuild Getting Sidetracked

I am a lot more interested in cleaning off the parts I need from Junk Bike. I cleaned off the front fender stay from Junk bike, which I painted Krylon Mid Blue to go on Blue Lite. And I took off the plastic cable guide that was on the old fender, that I need for Blue Lite's fender too.

I tightened the spokes on Junk Bike's front wheel.  Some of them are sticky with rust, so I backed off a few threads, added oil and retightened.  Then I pumped up the tire, which is still holding air one hour later.  But the tires had water in them that got forced out because of filling the tire with air.  Also, the rim strip inside the wheel was partially out, so I cut it off.  It will need to be replaced later.

I added 150 cc of fork oil and ATF  to each of the forks, and cleaned out the area just around the fork oil seal which was full of junk and water.  I checked the straightness of the forks by holding the fork leg and turning the tube. If the forks were bent, the top of the tube would move around in a circle, but it looks like it does not move around.  The real test will be after I install them on Blue Lite. I am planning to flush out this oil and put Synthetic engine oil in the forks before mounting them on the bike.

Cylinder Glaze Breaker

After trying to break the glaze in Junk Bike's cylinders by hand, I could see there was some light pitting due to corrosion in the right cylinder.  I decided to buy a glaze breaking tool, (Lyle Stone Type Glaze Breaker #23500 - 2" to 7").  It barely fits the 2" CD175 cylinder. It does a nice job of removing glaze, but some pitting was still visible on the cylinder wall after I worked it for about 20 seconds.  Also, my drill runs at 2000 rpm, and I can't push and pull on it fast enough to create a cross hatch pattern. My pattern is mainly straight around the cylinder wall.  You also have to be careful to not drag the tool straight out of the bore, it will make vertical scratch marks.  To get the tool out, I stopped the drill then twisted it out leaving a spiral mark like a cross hatch.  I used WD40 as a lubricant while running the glaze breaker.

Remember Wash the cylinders out with hot soapy water. And, if I ever get it running, break in the engine without overheating it (Let it cool down several times).  Do not use synthetic oil until it is broken in.

More On Gasket Removal

The razor scraper is excellent for removing gaskets.  This time I started removing the base gasket with this tool, and instead of taking 3 days, it took 20 minutes.  And the surface is probably smoother when I'm done.  I just have to be careful to avoid nicking the edge of the machined surface, keep the blade sharp and at the correct angle and it works like magic.  It even shaves off aluminum burrs that may be sticking up.  Actually, I got the gasket off in about 10 biggish pieces, then went over the surface with the razor to clean up the little sticky bits that were left.

January 23, 2003

The Fenders and Turn Signals

I found the bolts I need for the front fender stay.  On Junk Bike, not too many bolts are the right ones, so I look at the parts book which gives the correct length then I look for it in my collection.

Then I removed the turn signals and tail light from the fender.  On the K4 CD175, the back fender has a wiring tunnel and harness that you can unplug the lights from, unlike the K3 whose turnsignals at the rear have a very long wire coming out of them that connects to the main harness under the seat.

Out of 4 turn signals on Junk Bike, I have one good Honda lens and one aftermarket lens that has a lighter orange color. I got only one decent lens screw, and it is rusty. I got four bulbs, one seized in place and removed after soaking with WD40.  No lens gaskets.  The turn signal posts chrome has mostly turned to rust and the nuts and washers are rusty too.  I managed to get the posts off the turn signal body by prying the gap open with a screwdriver while pulling on the post.  The turn signal body has no serrations inside to match the serrations on the post, the bolt must be tight to keep it from spinning around.

To make Blue Lite look more like my first bike,  I plan to put the shorter rear posts on the front signals.  The rear post has a thick shoulder that will not fit through the headlight shell.  If I  enlarge the hole a little, it would fit. I would also need to a piece of inner tube as a shim to get it to tighten up properly, and that is probably a good thing to help stop cracking of the headlight shell.

I tried soaking a rusty post with naval jelly (phosphoric acid) to remove the rust, then sprayed it with Krylon Chrome.  It looks much better than rust, but you can still see the roughness and pits under the paint.

Junk Bike Goes Into the Basement

For me to bring a bike into the basement the second biggest obstacle is the stairs, where they are steep, narrow and have a couple of sharp turns. (Mary Ann is the biggest obstacle, of course) With the front end off and the engine out, I took off the handlebars and headlight and brought the rest of the bike inside and down the stairs to the basement single handed no problems.  Then I took off the rear wheel and the corroded rear brake.  I laid the frame on its side to do some work and found about 100cc of dirty water leaking out onto the floor from inside the frame.

Some things I noticed: Frame number CD175 3003335 (easy to remember) made in March, 1972.  The handlebar clamp threads are partly stripped. Lots of corrosion (white powder) inside rear brake, and the shoes are a most heavily worn about halfway between the pivots.  The tops of the foot peg rubbers are nice, but the bottoms are cracked lengthwise.  The steering bearings are no good, it feels lumpy to turn.  Some of the electric harness sheaths started cracking when I tried to bend them in the cold outside.

The swing arm will not come out easily. It is held (sort of)  in place by some frame plates even though the shaft is missing.  Last year I nearly lost the shaft on Blue Lite at 60 mph, and now I thank Honda for designing it so that the swing arm does not simply drop out if the shaft goes missing.  You have to give is a special twist to get it out, after loosening the center part of the chain guard

January 26, 2003

Junk Bike is practically down to the frame now.  The one remaining problem is getting the brake pedal lever off the center stand shaft.  It seems just as badly seized as Blue Lite's pedal was, but the frame bracket is not as badly worn. I took off the air filter box, and found a nearly new air filter inside, along with the usual spiders nests and dust.

I disobeyed my personal rule of restoration that says "Do not permanently alter the bike".  I enlarged the holes in the headlight shell, so that I could fit the shorter rear turn signal posts on the front.  I think the shorter posts look better, and they allow me to put rubber gaskets where they can protect the plastic of the headlight shell. Now I just have to make sure to keep that headlight shell together with the rear turn signal posts and rubber gaskets. Also, it probably will still work with the front posts, but just a bit looser fitting.

Later, I removed all the screws on the right hand cover of Junk Bike's engine.  According to a tip I saw on the internet, I placed all the screws in holes in a styrofoam tray, in the correct position.  I got them all out without drilling, because most of them are accessible to Vise Grip pliers.  But now the cover itself is still stuck, and apparently they may be collars in there to help position the cover, so I have to be careful to pull it straight out, and not lose them.

The newly blue painted front fender stay from Junk Bike went out to the garage to be bolted up to Blue Lite's fender.  I am now amazed at how clean Blue Lite looks, after working on Junk Bike for about three weeks.

January 27, 2003

Removing Right Engine Cover

rhcoveroff.JPG (222386 bytes)Click on the thumbnail for a good detailed picture of what's under the right engine cover.  This is Junker's engine.  All eleven cover screws came out without drilling.   I bought a big rubber mallet and heated the cover with a propane torch then tapped all around until I started making some progress.  Then I also had to carefully use a sharp gasket scraper to help separate the cover, and also a large screwdriver, even more carefully. 

There are some things to keep in mind for next time. At the bottom center of the enlarged picture above you can see the cutout where you can tap the cover off with a rod from the other side, but I didn't know it was there until I got the cover off. Also, there are locating collars around two of the case screws.  Also in the enlarged picture you can see a missing bolt which is actually through the main oil gallery, and is going to cause me a lot of grief because I will not notice it is missing until I start the bike next month.

I wanted to see what the oil pump screen looked like, and there it is at the bottom right, and you can see it is not clogged, but there are a few particles stuck in it.  At this point I could remove the oil filter and clutch to examine them, then clean everything up and maybe repaint the cover. I should also remove the oil spinner and replace its screw with a socket head screw.  I have a new gasket to put on it, the old one came apart. I also need to get the remains of the three spinner cover screws out, they were drilled flush.

rhcoverpainted.jpg (132214 bytes)        2 rhcoverpaintedscrews.jpg (69010 bytes)  In these two pictures, you can see the cover from Junk Bike painted with Krylon aluminum "High Heat and Radiator" spray paint, and compare it to Blue Lite's engine with the original finish.  In picture 2, I added the spinner cover (not yet polished). The screws I want to use are in picture 2, the new black socket screws for the big cover and new Phillips oval machine screws for the spinner cover.  The aluminum paint actually looks lighter than the factory finish to me, but in the digital photo it seems darker, which is strange.  

January 28, 2003

I didn't need to remove the clear coat to polished the oil spinner cover, but on the other hand, there was some corrosion and pitting.  I used rubbing compound with the Dremel tool, and then by hand to eliminate some of the funny marks left by the Dremel.  Then I used Mother's Three Step Wax, which got it to look good in real life, but not in digital pictures.  

I wanted to replace the original and buggered Phillips screws on the main right hand engine cover.  I cut some 50 mm socket screws to the right length using a hacksaw, and finished the rough edge off using the Dremel tool's cutting disk attachment.  The trick is to grind the threads in a direction that pushes the burrs to the tip of the screw.  All the screws threaded in easily after that was done. The two longest screws were cut to 45 mm, and the other nine were cut to 36 mm.

 I will have to remember to cover the brake pedal with a cloth when I install the engine in the frame, or it will scratch the paint for sure.

Cross Hatching the Cylinder Bores Again

The cylinder glaze breaking I did last week was not going to help the engine break-in because  I used a single speed drill at 2500 rpm, and the result was no cross hatch.  Now I have a reversible variable speed drill, so I did it over.

First, you cannot reverse the drill, because the glaze breaker will unscrew and fall apart. Maybe I should have got a drill with better speed control.  I found it hard to keep it to a low speed while pushing the drill up and down.  But the final result is much more satisfactory than the previous job.

January 29, 2003

I took out all the spokes for the back wheel.  I managed to unscrew all but one, which snapped off. I'm sure if I had used a propane torch I could have got that one off in one piece too.  Only 3 were not severely rusted.  The sprocket had to come off to remove some of the spokes. It looks good, and I can use it for a spare.  There was a lot of rust on the brake drum.  I tried to clean it off with the Dremel, but it look like it might need to be put on a lathe to make it smooth. The whole drum is about 6 inches in diameter.

After cleaning up the parts a little, I found the tube and rim protector strip were good.

Center Stand and Brake Pedal Pivot Shaft Removal

Next I went back to the rear brake lever.  Now I have a wedge that can drive in between the frame and the lever arm, so I heated up the lever with a propane torch, put some water inside the tube and hit the wedge, but still no luck.  It also will not twist when I put vise grips on the other end of the tube.  

I want to salvage the pivot shaft for Blue Lite more than I want the brake lever, so I began to saw the brake lever until it freed up. I needed to cut a slot in the brake lever so that it would release its grip on the shaft.  I started by drilling a pilot hole where I wanted the slot, then used the Dremel cutting wheel to finish cutting the slot.  I managed to cut about a 2 cm long notch in the brake lever, then I hammered a chisel into the notch to open it up.  With the chisel in there, and some tapping, the shaft started to move.  Next I had to use the dremel tool again to grind down the shaft surface so that it was smooth enough to fit through.  With 30 minutes more hammering, grinding and oiling I got the pivot shaft  off the bike.

January 30, 2003

I found the "Chilton's Motorcycle Owners Handbook" in the library today.  From 1979, it seems applicable to CD175 technology.  One particular tip I saw for the first time is to take the rich plug reading  from the ground electrode, not the center electrode. 

Lapping and Installing the Valves

I was lapping Junk engine's valves this morning.  The right exhaust the seating area is very narrow in one place.  It looks like corrosion has taken a bite out of the seating area in that spot.  I will just leave it like that and see how it works. Some of the other seats looked like they had some pitting too.  The valve faces on the K4 do not have the nice slot like Blue Lite, so I couldn't use the screwdriver to do the turning back and forth.  Instead I used a piece of hose.  The smallest I found was one quarter inch hose, and I had to jam another piece of inner tube into the hose to hold the valve stem securely.

Then I washed the head and all the valve parts in soapy water, pushed an oily wad through the valve guides, oiled the valve stems and started reassembly.

The Haynes manual has a reasonable diagram of all the little bits, but I still had to do some thinking and I was glad I made a sketch myself when I took them apart.  It was easy to get the keepers in once I discovered the trick. They fell in place all by themselves (almost), if I adjusted the spring compressor to the right height.  It was a lot easier than I hoped, and all four valves were done in less then an hour.  There were times when I might have lost a critical little bit, I was really lucky that I didn't drop any where I couldn't find them.

One problem I had was in my top end gasket kit.  I had thought the valve seals would be included, but they were not in the "Clarke Simpkins Top End Gasket Kit".  It does have the washers for the top dome nuts, but then I had already bought 100 of those, and I don't then they wear out anyway. Then I remembered that the oil seals from Blue Lite were in good shape.  Otherwise I would have just gone with no seals.

February 2, 2003

Installing the Camshaft

While installing the camshaft, I put screwdrivers into the stud holes to make sure the rocker shafts didn't slide in to block them. It does not seem to be much of a problem on Junker's motor, but I remember on Blue Lite's motor, the rockers do move in as I tighten the cam bearing screws and pinch the studs so the cylinder head cannot be installed or removed until the cam bearing screws are loosened..

I changed the four Phillips screws in the points housing for Allen head socket screws.  Here I discovered a problem.  Because the hex screw heads are higher, the top two screws hit the advance mechanism.  So I put the original Phillips screws back in for the top two.  Actually, the top two can be loosened with vise grips, so using Phillips screws there is not too inconvenient.

The advance mechanism was dirty and seized, so I took it apart and cleaned it.  I used lithium grease on the main bearing and oil on the other bits.  By turning the 8 mm bolt that holds on the advance mechanism, I can turn the camshaft and test that it rotates freely.

I used a new gasket on the right hand cam bearing plate.  I got a new blade for my razor scraper, and it did a nice clean job or removing traces of the old gasket.  I decided to re-use the left gasket on the points housing and the points cam oil seal.

Beginning to Reassemble the Junk Engine

We are starting to get warmer weather, some snow is melting.  So it's time I got at least the Junk engine together and into Blue Lite's frame ready to test start.  The head is ready to go on, but the lower engine needs to be put together first.  I cleaned off the gasket areas for the cylinder base and the right hand engine cover.  Then I tried to clean some of the particles out of the engine.  It's quite difficult without splitting the cases, but I decided to just try to clean what I can see, then change the oil frequently after I have it running, until it comes clean.

I cleaned out the oil spinner first.  It has about as much crud as Blue Lite, so I assume Blue Lite also has about 20,000 miles on it.  The screw came out easily, and I replaced it with a socket screw. 

Then I was concerned about the dirt I could see behind the oil pump, so I tried to remove the oil pump.  That was a mistake. The pump will not come off until at least the clutch is removed, and I was not prepared to take that extra step.  I broke a lock washer trying to remove the pump, and I don't have any spare tabbed washer like that.  I managed to pull the screen off the pump but it was hard to get it back on without breaking one of the plastic tabs.  I was lucky to not break the screen trying to squeeze it onto the pump while it was in the engine.  At least I had a chance to clean out the particles behind the pump. Also, according to the book, the gasket behind the pump needs to be replaced also, but I didn't see one, so I didn't replace it.

February 3, 2003

I fixed the broken tab washer with a piece of tin can. I made a hole in the lid of a tin can, cut around it with tin snips and fit the new washer under the old tab washer.  Then I folded up the edges of the tin can and hammered them tight over the bolt head.  

The hardest part was actually putting the engine (clutch) cover back on because it is big and hard to align all the holes in the gasket. It was worse because I forgot to punch out one of the screw holes in the gasket.  Hope I got out all the other bits that were supposed to be knocked out. These gaskets are cut, but many bits of gasket need to be knocked by hand out before installing. It's actually pretty critical if there is a hole that need to be knocked out because its an oil passage.  I guess you will never know you missed it until the engine seizes.

I cleaned off the oil drain plug and fitted a new o-ring, one that came in my gasket kit that is actually for the valve inspection caps.

Reassembling the Engine

Next I started preparing to lower the cylinder over the pistons. I think a check list is needed.

  1. Cam chain threaded through the tensioner, with ropes attached holding the ends up
  2. Tensioner arm and guide rollers bolted down tight with lock washers.
  3. Base gasket with the big holes at the back
  4. Pistons with rings right side up and in the right order.
  5. Pistons installed with two new circlips each, pins oiled and wrist pins oiled. 
  6. IN mark on the piston at the back. 
  7. Oil the cylinder walls

I used the left over quarter inch hose (from valve lapping) to hold up the pistons while I lowered the block.  I used a pick to push the rings into the cylinders, and it required patience and no forcing.  Also, I did not use a ring clamp tool.

I just found out the top and second rings are not the same.  According to Clymer, the middle ring is 'stepped'.  According to my 1968 CD175 shop manual, the second ring has a scraping surface at about a 1 degree angle from vertical, while the top ring has a vertical scraping edge.  Also, the second ring is 1.18 mm thick, and the top ring is 1.17 mm. I can't see the 1 degree angle even with a magnifying glass, but I was able to measure the thickness with a micrometer.  I get 1.185 mm for the ring marked N, and 1.17 for the ring marked 1N.  So I think the micrometer has identified the 1N as the top ring.  According to a website I found, the ring technology is incredibly important to long lasting rings.  Piston rings are arguably the single most important technology that have allowed internal combustion engines to dominate the field.  It may also be a coincidence the Soichiro Honda started out making piston rings for Toyota.  And the factory manual feels it is worth devoting 2 pages to piston rings. Click here [EXTERNAL] to go to the Piston Ring Museum website for more than you ever wanted to know about piston rings.

With the new pistons, I installed the ring marked 1N at the top, but I don't see markings on the used rings.  They are the same thickness and probably worn so much it does not matter any more, so I'm just going to leave them as they are.  The groove clearance is supposed to be less than .004", and I measured it at .003".

Next comes the Cylinder head. 

  1. First step. read the Clymer manual.
  2. Put on the head gasket
  3. Put on the rubber rings and the 4 locating dowels
  4. Install the tensioner pushrod in the head with the spring compressed.
  5. Turn the pistons to top dead center.
  6. Turn the camshaft so the "o" mark is top dead center.

I followed the checklist above but still forgot to put in the tensioner pushrod.  I had to remove the head and put the pushrod in, then drop the head down again. I tried to connect the cam chain, but when I finally had the clip in, I found the crankshaft had moved from TDC.  I was lucky on the third try, and everything fell in place.  The cam chain now has the master link clipped in place.

Now Things Go Wrong

Now I remember that I forgot the two locating dowels for the oil passageways.  I will take off the head one more time and put them where they belong.  As I am pondering that thought, I watch the engine, now heavier with the cylinder head, start to roll forward off the workbench.  If I hadn't caught it, that would have been about 100 pounds of metal colliding with the floor, and no bolts to hold it together.  Always just on the edge of disaster.

Ready for the Final Inspection

After waiting till my karma was settled, I removed the cylinder head again, put in the two missing dowels, and put everything back together.  I didn't try it, but I am convinced I could thread a new cam chain in there without removing the cylinder head if I had to.

February 4, 2003

I turned the engine over using the rotor bolt.  The cam shaft turned and no valves hit any pistons.  I loosened the cam chain adjuster bolt and watched as it sprung into place. The cam chain, after adjustment, is not as tight as I  expected it to be. I can easily deflect the cam chain with a screwdriver, but not far enough to touch the inside of the cases.  I will compare it when I install Blue Lite's cam chain.

I installed the points and condenser, did an adjustment of the valve clearances.  Finally I did a quick check of the timing, just looking to see when the points separated.  

 The things I can check before installing on the bike.

  1. Install extra head bolt (28 mm x 6 mm?).  It looks to me like the head bolt on Junk (the K4)  is actually 8 mm diameter, but the K4 parts manual does specify 6 mm so this is an unresolved mystery. Also, to make things worse, the head on a 8mm hex bolt is too big to fit in the space.  The only bolt I can think of that would fit is a socket screw (using an Allen key). Of course I don't have one.
  2. Install extra cylinder bolt (25 mm x 6 mm)
  3. Torque the head bolts
  4. Fill with oil.
  5. Check oil flow through the top rear outside cylinder bolts

Torque the Cylinder Head Bolts

The old CD175 with the sloper engine calls for 11.6 to 15.2 ft. lb. for the cylinder head bolts. In that bike, the head is not only bolted to the frame, but there is no frame down tube, so it is the only frame structure.  The Clymer manual specifies 11.5 to 14.5 ft. lb. for 175 twins 1964 on). I went to about 15, and I used my "Indestro" torque wrench using the order specified in the Honda manual.  

I polished the rotor cover, scraped off the old gasket, put on a new one, and put one o ring on the very bottom screw.  If the other screws leak, I will put on more o rings.

Later on I will add oil and put the kick start lever on to see if I can build up some oil pressure and combustion pressure.

Fixed the Missing Head Bolt. 

I don't have the bolt that is hidden between the mounting brackets on the engine top cover. I remember now, the head cover was off when I got the bike and all the bolts and screws were missing. Tom (who gave me the Indestro torque wrench last year) called while I was working on it.  He had a suggestion of how to fix it without shopping for a new bolt. "The oldest trick in the book" he called it.   I guess somebody stripped the original 6 mm bolt then drilled and tapped a bigger one, with a thread (I think), 1.25 x 8 mm.  So I found a suitable bolt and ground the head smaller so it would fit in the space, then I hack sawed a slot in the top and tightened it with a straight screwdriver. Not very pretty, but nobody can see it.  The reason I need this bolt out is because it  reinforces the area where the engine top is bolted to the the frame.

February 4, 2003

I went back with a ohmmeter to check the ignition timing, and found the points were not passing electricity.  I used a small file and now they seem to work fine.

The carburetor is attached now.  I readjusted the float level to 28 mm.  Last summer I had it set to 25 mm, and that might have caused it to run rich (from looking at the the condition of Blue Lite's combustion chamber and pistons.)

I added 10W-40 plain oil, and tested the gear shift.  I could get it to change between 1st and 2nd, and into neutral, but I couldn't get it into any upper gears.  It was the same on Blue Lite's engine, so I need to mount it on the bike to check the transmission properly with the clutch lever attached.

February 6, 2003

The Junkers engine is ready to go into Blue Lite now, but the weather has turned cold again.  So I spent the morning painting the front fender and headlight nacelle using a gray primer.  I also completed putting together two short turn signals to go on the front.  I still can't figure out why the paint on the Junk bike looks like silvery crocodile skin where it's faded.  It almost looks like a PO attempted to spray silver paint over the candy red, and the new paint turned bad.

I bought a can of 'Old Cat Yellow' for Caterpillar tractors, and painted the headlight nacelle.  The paint is a bit rough, but I can sand and polish it later.  Click here for a look at the paint job, the short turn signal stalks and an inset picture that show the proposed paint scheme (done in Corel Photo Paint). 

I removed the original front tire.  The tube was still holding air, but the tire had radial cracks in the rubber.  It was still wet inside the rim, even though it has been inside the house for the last 3 weeks, and lots of rust on the inside of the rim.

February 6, 2003


I tried putting in a new spoke I bought last summer.  It did not fit the rear tire then, and didn't fit the the front either, still too long.  And it does not bend far enough at the hooked end.  That's probably what happens when you try to put in 'inside' spoke in an 'outside' hole.

I also tried putting a rear spoke in the front wheel.  That doesn't work because the rear spoke is too thick, but they are about the same length as the front spokes.

February 10, 2003

I went over the spokes on the front wheel again, because I am going to use Junker's front wheel  this summer.  The drum is in much better shape than the one on Blue Lite.  On Junker's front wheel,  I mounted the 3.00x17 Bridgestone rear tire that came with Blue Lite, put in the Inoue 2.75/3.00x17 tube and rim protector that were in the Junker's rear tire.  That Inoue tube is actually bigger than the Nitto tube that was in the front tire (3.00x17).

I did a lot of wire brushing and cleaning of the inside of the rim, and finally painted it with spray can primer.  Also cleaned the rear rim at the same time.  I think there was less rust than Blue Lite inside the front rim of Junk Bike, at any rate there were no curled up sharp bits of chrome.

Finally I filled the tire with 30 lb. of air and wrapped soldering wire around a spoke to balance the wheel.

Blue Lite Valve Oil Seals

I started by washing all the valve parts in soap and water.  There were some rubber o rings that I thought were the oil seals for the exhaust valves.  Actually, the "Valve stem seal" is a metal? (at least very hard) part, and the rubber part is called "Stem seal rubber cushion".  Since I used the rubber cushions from Blue Lite in the Junker's engine, I made up some new cushions by cutting an inner tube to make two little washers. I think the only purpose for the cushions is to hold the seal tight.  And actually the seals do move up and down a bit if mounted with no cushion.

The rubber o ring cushions that I thought were in the full gasket kit are actually the o rings for the rotor cover screws (there are three of them).

The 1968 shop manual does not show seals on either intake or exhaust. Why does the 1968 and later Honda 175 have exhaust oil seals but no intake valve oil seals? First of all, I can see the exhaust stem is not sitting in a pool of oil, which might have been a valid reason for an oil seal.

There are valid reasons for using seals on the intake valves.  Oil lost through the intake valve goes into the engine and fouls plugs, and carbons up the combustion chamber. Also, the intake valve can be partly lubricated by fuel mist, and so does not need so much oil from above leaking down the valve stem to lubricate it. Finally, the intake valve stem is subjected to vacuum sucking oil through, but not the exhaust.  In the exhaust valve, oil could be blown back up the stem by the pressure pulses.

There is at least one reason for not having an oil seal on the exhaust valve. The exhaust valve needs more lubrication because of the heat, and not having an oil seal can help lubricate the stem. And a bit more oil out the exhaust might even help keep the mufflers from rusting!

Some people do not install the oil seal when doing valve jobs, just to make sure the valves are lubricated. I am going to stop reassembling Blue Lite's cylinder head until I can decide what to do next.  My choices are (order of preference is not known)

  • leave the seals and cushions out
  • buy new seals and rubber cushions
  • put in the home made cushion made out of inner tube rubber.
  • Use the neoprene o ring from the gasket kit. (more heat resistant, but too thick)
  • Use 1/4" o rings from the auto parts store
  • wait until Junker's engine needs a teardown and get my seal cushions back out

NOTE: I bought 0.25" o-rings, but they were too thick in cross section. So I laid some rings flat on the workbench and used a razor blade scraper and sliced off almost half the thickness of the rings.  It's tricky, but I had a couple of extra o-rings to practice on until I figured out how to do it evenly. I was hoping to get two rings out of one, but then I realized that I was not that good at slicing.

The Gas Tank

I do not put many warnings on my web pages, but gas tanks really scare me.

CAUTION: Even if the gas tank is rinsed out with water several times, it can still contain enough vapor to explode if exposed to heat. It is possible even if you are sanding the tank to create heat enough to touch it off, let alone when welding it.

Apparently the quick and dirty repairs to a gas tank with pinhole leaks are either epoxy glue or sheet metal screws in the pinholes with a gas proof sealer around them.  I washed out the inside of the tank with soap and water.  I need to seal up holes I know about and then check for other leaks.

I removed the chrome side panels, and found dirt under them, and some rust spots.  One spot on the tank looks really bad, hope it is not another leak.  The paint under the cover is not faded, but does not look really good either.  There is also rust on the chrome panels where it can't be seen when everything is back together.

I bought some  Motomaster brand "Liquid Metal".  It claims to be gasoline, oil and water proof.  It  contains Methyl Ethyl Ketone.  I am going to seal the pinhole leaks in the gas tank with this stuff, and hope it works. I think it is safer than soldering or welding.  I hope that sanding the tank will not touch off an explosion.

I started by using the rough sandpaper disk on the big drill.  That cleaned off the main area where the pinhole leaks are, but left rust in the pitted areas.  Then I got the Dremel tool with a small pink stone attachment, on medium speed, which made short work of cleaning out the pits.  It also completely finished off the stone on the tool, there is almost nothing left.  Then I washed the area with soap and water, wiped it off with a paper towel, and spread on a thin layer of the Liquid Metal.  It's supposed to dry in 4 hours in 21 deg C, so I turned up the furnace a bit too.

I also got an idea about a better way to clean out the petcock.  The reserve passageway clogs up too easily with rust particles.  It needs to be as wide as possible to let the particles through and let them get trapped in the sediment bowl instead.  Otherwise, you will end up pushing the bike home when it goes on reserve.  So I got a drill about the same size as the hole and twisted it into the hole by hand.  It's slow, but it gets the crud out much better than with a needle. Now the hole is back to its full size, and I'm sure it will pass most of the little bits of rust down to the sediment bowl.

February 15, 2003

More Gas Tank Cleanup

The Liquid Metal cured overnight, and I filled the tank with soapy water this morning.  Four hours later, no leaks had appeared, so I began draining with the petcock open.  Slightly brown water came out, and within 10 minutes the output slowed to a trickle.  The screen did not look clogged, but when it was removed, the flow went back to normal.

Now the tank seems to be holding water, I will try cleaning it up and use it next summer. I tried sanding off the cruddy paint layer on top of the tank, and found the original "Preserve Nature" label under the cruddy top paint layer.  I heated up the label and tried to scrape it off with a razor scraper.  I got one fairly large piece off, the rest came off in little bits.

I decided to try cleaning the inside of the tank without using acid. I tossed in my handful of rusty nuts and bolts, this time with 4 cups of hot soapy water. It was necessary to plug the petcock which I removed for fear of breaking the inlet tube inside the tank, so I plugged it with a screw and a foam ear plug.  I shook up the mix and emptied the water about 10 times.  Each time it came out dirty.  Checking inside, I could see the rustiest area was the top of the tank, so I put more effort on scrubbing that part.  Finally I dumped the nuts and bolts, rinsed out the tank about 5 times. Each time more black sediment came out, until the water started coming out clean.  But it still smells of old gas. And I still can see a lot of rust inside the tank, but it's better than it was before. And now my nuts and bolts are also clean.

February 16, 2003

I am drying the tank with a hair dryer.  I give it about 5 blasts a day lasting a couple of minutes each.  There is a little bit of air cross flow because I have the petcock off.  I have a coating of primer on it and on the chrome panels to prevent further rusting.

The Handlebar and Throttle Grip

I was hoping the Junker's handlebar would be better than Blue's.  Blue's handlebar has a couple of big gouges in the chrome.  Also, Blue's right hand control  has a twist throttle instead of the original screw throttle, and there is no threaded hole for a mirror on the right. And I also think that Blue's  handlebar has been bent a little.

But the Junker's throttle cable is frozen and I have not been able to free it up yet, it also has a lot of cracks in its outer shell.  The chrome on the  handlebar has many very small dots of corrosion that don't go away with steel wool.  It still looks good from a distance, but except for the gouges, Blue's chrome is better. 

It was difficult to dismantle Junker's handlebars. I broke the wire to the starter button taking it apart, and other buttons and controls are corroded. Because of the frozen throttle cable, the throttle grip was very tricky to get off.  What I didn't know was that in addition to having a frozen cable, the screw mechanism also was jammed.  I finally managed to get the throttle out with no other damage.

The frozen throttle cable took a lot of force to start it moving even when it was off the handlebar.  Finally I managed to slide the throttle cable back and forth inside the sheath, but it feels very sticky either from rust inside or some cable wires are broken. The cable sheath is 34.25" and the overall length is 36.75".  I see some on eBay that look the same (Like a CA200) but I need to verify the length. I thought I had a spare throttle cable from Matt, but I don't see it in my parts box.

The throttle grip is called the "Throttle Grip Pipe" and it has a screw ramp molded inside for pulling the throttle cable.  The throttle grip pipe is very rusty inside and sounds like gravel when I turn the hand grip.  I was tempted to take off the rubber grip to clean inside the other end, which is the worst part, but the rubber grip is really stuck on there, even with soap and hot water it won't budge.  

Greasing the Throttle Grip

The side of the right hand switch housing has a bearing surface that fits the throttle grip pipe and holds it in the right position as it turns. There is another bearing surface for the throttle grip at the outside end, looks like it is molded into the end of the rubber hand grip. Between the two ends, the throttle grip pipe does not even touch the handlebar, the two ends are where the cleanup and the grease is needed, and of course on the slider.  When greasing the outside end of the handlebar, it would be a good idea to grease the last 3 mm inside and outside.

Playing with this grip, I found that it takes a lot of effort from the carburetor end of the cable to make the grip return to closed position.  Actually I simply could not do it at all.  So I think these  screw throttles have to be in almost friction free condition before  they will close by themselves  when you let go of the throttle grip.

The threaded holes for the mirrors are slightly stripped on the left, and a bit better on the right.  I used a 1.25 mm pitch thread chaser to clean them out a bit and now I can thread a mirror into either side.

February 18, 2003

The Engine Goes Back In Blue Lite

Temperatures were just below freezing today, it felt like summer compared to the last couple of weeks.  It took me three hours to get the engine in, including mufflers. I did the job alone, but used a hydraulic floor jack.  Near the end of the job, I had just one bolt left to go in the top front bracket, but I couldn't get it in, the hole was not lining up.  Finally I moved the floor jack to the back of the engine, lifted a little and it lined up and the last bolt went in.

I don't know how I would get the engine in single handed without some kind of  floor jack, but a  scissors jack would be better in that it is easier to move it up and down while trying to line up bolt holes.  The hydraulic jack is a one-way operation and needs some fiddling with the bleed screw if you go too far.

Before trying to start the motor, I still need to connect the gas tank, put on the air filter, put in the battery, and add gas to the tank.  Also I need to slip the breather hose onto the top of the engine (probably need some heat). Also, connect the electric plug from the engine.

Before it will drive, I also need the chain, the rear brake rod, the seat, the starter cable and the foot pegs. I should also tighten up all the battery connections and the vent hose, and put clamps on the carburetor intake pipe.

February 19, 2003

Starting the Junkers' Engine

The neutral light is not working (maybe I forgot a connection), but I was able to get the gears into neutral using the clutch and turning the drive sprocket by hand.  It feels like all the gears work properly if the clutch is pulled in.

I connected the battery, air filter and gas tank.  I added gas, and kicked.  It wouldn't start at first but I put the hair drier on the carburetor at full heat for a couple of minutes, and then it started.

Why You Should Think Like The PO

I didn't rev it up much, just kept it going by playing with the throttle and choke. When I shut it off, after less than a minute, I saw a pool of engine oil on the floor about 30 cm across.  Apparently the Previous Owner had removed and lost a crank case bolt that runs through the main oil passageway. When the engine is running, the oil pump feeds all the oil directly out this hole.  It happens to be the longest bolt, 8 mm x 135 mm  (part number 90003-302-000), located at the right front corner of the crank case - and I don't know if I will be able to get a bolt in without taking the engine out again, because it is very close to the frame. I also should be checking all the other crankcase bolts, I suppose.

It was pretty obvious already that this bike has been molested, for example, the swing arm pivot bolt and nut had been removed and lost forever.  A psychological profile of the PO would indicate a tendency to remove vital parts, then immediately lose them. Among motorcycle restorers and salvagers, PO is short for "Previous Owner" - if there was more than one PO, it refers to the one who did the tampering.  Sometimes the PO is not actually the owner, but a psycho amateur mechanic "helping" the owner. It is important for the restorer to try to understand what PO might have done. 

One reasonable explanation for the missing stuff is that this bike was already used as a donor bike in some other worth while project.  However the story I heard from Tony, who sold me the bike, makes me believe this was more a case of  thoughtless wrench twirling.  Because this bike is a non runner some extra things will need checking if I want to actually run it instead of just using the engine for parts.

Luckily there was a sheet of plywood to catch the oil, because otherwise it would be on the carpet, and I think I lost all the oil the pump could suck up.

Engine Comes Out Again, Goes Back In Again

I borrowed the correct crank case bolt from Blue Lite's motor, and I went out to the garage again for 2 hours to get everything back together with the missing bolt in.  I had to remove every engine mounting bolt, the mufflers, and the air cleaner.  I could not simply pivot the engine up on one of the the back mounting bolts because the missing crank case bolt was too long and the engine can only go up about 5 cm..  I had to swing the engine to the right about an inch to clear the frame tube and then I could slide the bolt in successfully.

Finally I tried to tighten the crank case bolt once the engine was back in, and I can't fit a socket on it or even a box end wrench.  I can only use an open end wrench. Then luckily I remembered to refill the oil.  I will wait until tomorrow to try to start the engine again and see if it holds oil and still starts.  I did not bother to check if any other bolts are missing because I am an optimist.

The Junkers engine is basically rebuilt, but you can go here to continue with the log of getting the CD175 on the road. And I plan to take Blue back to Grand Bend, the place where the cam chain broke.

April 9, 2003

Reassembly of Blue's Engine

In the last few weeks, Junker's engine has worked fine for the first 300 miles of riding.  Good compression, no oil leaks.

Right now we are socked in with ice and snow. I was watching the fall of Baghdad this morning on TV, but took time to reassemble Blue Lite's engine too.

I bought a $7.00 metal ruler to check the cylinder head for for a flat surface. It seemed like there was a gap under the ruler near the middle, enough to allow a piece of foil to slide under it.  I will leave it the way it is, I don't have any real flat surfaces to fix it with anyway, I also measured a mirror surface, and it was also curved according to my ruler.

Yesterday I redid the cylinder deglazing over the job I did by hand, using my variable speed drill and the deglazing tool.  There are still a few vertical scratch marks and horizontal marks visible, and there is also a slight ridge at the top of each cylinder.  I decided it's OK to leave it that way. After all, Junkers cylinder didn't look perfect either.

Then I installed the valves using my shaved 1/4" o - rings as exhaust valve seal cushions.

Assembling the cylinder head was more trouble than Junkers, because of the previous problem with the points housing jamming on the rocker pivot shafts.  I had to keep the cylinder stud holes free and clear while tightening the screws on the points housing.

I still need to install the new pistons and rings, and to dress the points surface and install them too. Then the timing and the valve adjustments will need to be done, and oil added to the engine. But the most important thing to remember is that I am missing an important oil gallery bolt, which was donated to Junkers.  Before I start up Blue's motor, I need to cannibalize that bolt out of another engine.

April 2004

Blue's engine is still sitting on the table one year later with no further changes. (This is now 2004).  I will continue the log when I do something more to that engine.

Click here to go to where Junker's engine gets installed in Blue's frame (February 2003)

Click here for an index of all the maintenance logs on my website.