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Discussion Starter · #1 · (Edited)
Hi there,

I picked up a 1972 CL175 without a title for $325. It has 6,500 miles on the odometer. The previous owner said he had stored the bike in a garage for several years before moving it outside.

I'm not sure how long the bike was outside, but it has seen the elements. Unfortunately, the muffler (which is my favorite part of the bike) is rusted straight through, so I have parts on the way to build a new one. Save for the muffler and a pair of corroded forks, the overall aesthetics of the bike are okay.

Carburetors are clean.

The motor is locked up. The right-hand spark plug seemed mostly clean, while the left plug revealed some gunk buildup. I've since pulled the motor out and have ordered a new gasket kit and piston rings.

I'm having some troubles in removing the valve head cover due to a tricky bolt placement, but I'll post about that below.

I wish I had taken some more photos of the assembled bike, but that ship has already sailed. Apologies for the sideways ones—not sure how to correct that.

Any input about this bike would be much appreciated!

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Discussion Starter · #2 ·
As for the bolt—I removed all acorn nuts, but there seems to be a 10mm bolt tucked away in the mounting bracket. My extended 10mm socket just won't fit. Is there a special Honda tool I'm missing?

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Sensei
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That "hidden" 6 mm bolt just requires a "skinny" 10 mm hex socket....I use a six-point, 1/4" drive, short socket on an extension.....
 

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Discussion Starter · #5 ·
Found a smaller 10mm socket and the valve cover came right off.

I have both the points and the tach housings off, but the chain is proving to be difficult to work with. Anyone with experience removing the cam?

Also, does anyone have the shop manual for this bike they could PM me?
 

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Discussion Starter · #7 ·
Not great news about the cylinders.

There is some pretty bad corrosion/buildup in both chambers. The pistons are about 1-2 cm down from TDC.

The cylinders are REALLY stuck on there. I've tried combinations of using a heat gun, tapping the sides with a rubber mallet, pressing the kickstart lever... no use. I seem to recall my CM400's cylinders had a lip on the bottom for prying off, but do the earlier twins not have that? Any tips on getting this darn thing off?

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I would suggest totally stripping the unit down, ie remove the side covers, clutch etc, then split the cases and remove the gear clusters etc, so that you are just left with the upper crankcase and crankshaft. With the case suitably supported, so that there is no load on the crankshaft, it may then be possible to tap the pistons down their bores.

If that fails, try some penetrating fluid, diesel fuel, etc, leave it to soak, see if that frees it off.

If all else fails, a hole saw in an electric drill will remove (destroy) the stuck piston.

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Discussion Starter · #10 ·
No pneumatic hammer, unfortunately.

This is the current stage of disassembly of the motor. I can't tell based on the language of the shop manual, but at what point can I crack the case open? Do I have to remove the outer clutch basket and oil pump before I can open the crankcase?

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I’ve had some luck soaking the tops of the pistons with a 50/50 mix of acetone and ATF (automatic transmission fluid) or MMO (Marvel Mystery oil). You’ll need to let it sit for days, tapping it lightly with a block of wood and hammer. Richards suggestion of splitting the cases might be prudent. Having the weight of the crankshaft might help to leverage the task. Keep in mind you want to ease the pistons out at the same rate.

The rust tends to etch the liners and you’ll need to measure them to see if they can be machined for oversized pistons and rings.

Good luck!
 

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Do I have to remove the outer clutch basket and oil pump before I can open the crankcase?
Yes, because the oil pump is bolted to the lower case half, and cannot be safely removed without taking off the clutch basket first. Yes, you could unbolt the pump and wiggle the pump plunger out, but it's not good practice.

The oil spinner has to come off in order to remove the crank gears which mesh with the clutch basket gear, you need a special tool to undo the crank shaft nut inside the oil spinner. Use a handle bar bolt ( or similar ) to draw off the oil spinner cover, don't try pulling it out with pliers.

On the other side of the engine, the generator rotor / starter clutch does not need to be removed.

When separating the cases, remember that there is hidden bolt beneath the oil drain plug. This caught me out first time I had a 175 apart.
 

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Discussion Starter · #13 ·
Thanks for the thorough response! I'll try giving it a go this afternoon.
 

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Discussion Starter · #14 ·
I've removed the oil pump, oil filter housing and clutch basket.

I'm now trying to remove the shifter components. The manual says I need split the cases to disassemble the shifter, kickstarter and other parts. But all of those parts seem to be interlocked in a way that would make splitting the cases difficult without removing them first.

Also, the impact driver couldn't even handle the phillips screws holding the shifter drum in place (top left). I would prefer to not drill out that screw and risk stripping the threads. Did I just create a problem for myself?

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Discussion Starter · #15 ·
Also, the case and cylinders are pretty grimy due to the decades-old oil. I plan on soaking most engine parts in a 50/50 mixture of simple green and water, followed by thorough scrubbing. To avoid corrosion, I'm thinking of simply blasting the parts with my heat gun while they lay out in the sun, followed rubbing all the parts down with MMO.

Does anyone see any possible chance for this going awry? I'm mostly concerned about the cylinder jugs.
 

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Sensei
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On the engine's left side, remove the circlip/snapring and special washer from the shift shaft.....You can then pull slightly downwards on the shifter pawls and the pull the entire shaft out of the engine.....

Having NO idea where you are located (you didn't add it to your profile or signature), All I can do is offer my phone number for further disassembly instructions....I'm NOT typing this all out for the umpteenth time.....
540-525-5199......
 

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Discussion Starter · #17 ·
Finally had the time to split the cases.

I could tell the kick starter was not engaging like it should. Turns out the kickstart gear is broken in half, which I heard is pretty common with these bikes. So I'll be ordering another one of those!

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After sorting all that away, I tried several different methods of dislodging the pistons from the cylinders. They are really stuck in there, but I'm really hoping to save the sleeves and pistons.

My current approach is letting the weight of the crankshaft pull down on the pistons while the crank case is supported by two wooden blocks. The piston heads are soaking in penetrating oil, and I'll occasionally blast the outside of the motor with the heat gun while and then tapping on the piston heads with a wood block and mallet.

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I'm really hoping I don't have to source new pistons and cylinders, but we'll see.
 

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Discussion Starter · #18 ·
FINALLY got the pistons out. They're toast, but the cylinders looks like they only need a hone. I've got new pistons on the way.

Next up—cleaning the engine head and lapping the valves.
 

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Discussion Starter · #19 ·
Also, anyone hunting for NOS standard bore 175 pistons should check this page on ebay. They were the cheapest I could find at ~$60 for the pair, and it looks like they have 5 left.
 
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