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Discussion Starter · #1 ·
All,

Just bought an old 1982 CM450C for $300 as a nonrunning-project bike. Previous owner did not have a ton of experience except, "I was riding one day, it made a loud funny sound and I had to walk it home."

Wasn't sure what I was getting into, but expected a little work. Previous experience for me is rebuilding an old '82 CB650, pretty much everything except taking the engine apart.

Started going through the electrical on the new bike and everything seemed to be functioning correctly, but when I pulled the carbs, there were metal shavings in the right carburetor locking the slide in place. I then looked into the cylinder head and there were a whole lot more metal shavings in there (see attached picture).

Obviously not good and I am not sure where to start. I'm guessing Ill have to pull the engine, but don't want to take it completely apart if I don't have to. Any starting advice/help would be greatly appreciated!
 

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If the valve stuck open due to wear / lack of lubrication. Next step would be to remove the head and look at the carnage.
 

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Discussion Starter · #7 ·
usually requires replacing parts - you can't tell what parts until assessing the damage
Can I inspect damages while it’s still on the frame, or do I have to pull the engine? Also, if it is the piston - is that something I can replace without spending more than what I paid for the bike?
 

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I don't know for sure, but the head can usually be removed with engine in frame - the cylinders usually cannot be removed unless the engine is out.
 

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I would start by taking the cam cover, flywheel cover and clutch cover off.

Horrible noise whilst riding bring bike to a Holt, and pushing it back home, does not sound good.

So pictures of camshaft area, flywheel area and clutch area.

Does the engine turn over by hand or is it locked solid ?

You know of CMSNL ?

If you invisage removing head/cylinders, penetrant every day on the 4 centre head bolts where they go into upper crank case...for a month...
 

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Discussion Starter · #10 ·
Currently out of town, but will add pictures when I get home.

I took off the left crank case cover and was able to rotate the bolt in the center of the fly wheel, but it only rotated 360 degrees counter clockwise and then would stop (I’d then rotate back clockwise to get to the starting point). I did have the valve cover off, and only the left side intake valves would move and the single right side exhaust valve moved, but I was not able to continuously turn the bolt on the flywheel counter clockwise. Guessing if it was functioning correctly, I’d be able to continue to rotate it?

Ill pull the engine as soon as I’m able to get the dang exhaust system off the bike. Got the header bolts off, the center bolts underneath off, and the rear foot pegs bolts off - so it’s completely loose but not coming off. I’ll search the threads, but keep me posted if there is a easy way to remove it. Thanks!
 

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It'll be easier to drain the oil with the motor on the frame. It will also give you an idea of what made it to the bottom end. I'd be afraid of damage to the con rod at least. Check for free play when you get the pistons out. For me, this would mean a complete teardown and reassembly to make sure there's no metal in the bottom end.
 

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Discussion Starter · #13 ·
It'll be easier to drain the oil with the motor on the frame. It will also give you an idea of what made it to the bottom end. I'd be afraid of damage to the con rod at least. Check for free play when you get the pistons out. For me, this would mean a complete teardown and reassembly to make sure there's no metal in the bottom end.
Oof, time to do some learning. I appreciate the tips, I did drain the oil as well but did not see or feel any metal in there. So hoping that is a good sign!
 

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Glitter in the oil ?

How was the oil filter ?

Exhaust joints...

They should contain a soft sealing short " tube" and a compressing clamp, but can be troublesome...

I would re fasten exhaust, then concentrate on removing silencers.

Penetrant penitrant penitrant, turn turn turn, turn and pull turn and pull and turn and pull off.

You get the idea.

Same for front pipes, which are/where free in head ?

Be prepared for anything in this motor, and the rest of the bike.

Look at your first picture, sealer...
 

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Discussion Starter · #15 ·
Just pulled the engine. Found a small piece inside the clutch cover, but no metal in the oil/oil filter. The attached photo shows the right side header from the front of the bike. I can see the bottom of the valve and it looks pretty messed up. Is this motor salvageable/worth rebuilding? I paid $300, so not too heart broken if not, but would certainly like to learn how to take it apart/fix it if it’s feasible!
 

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It’s definatly worth pulling apart. Replacing a valve is a bit tricky. It has to be compressed to remove and then the new one lapped. IMO, it’s well worth it just to get the experience/knowledge.

It will need a good cleaning. Get all the metal shards out. Check the freeplay on the crank/conrod. If it’s not too loose or bent, then you should have a relatively cheap repair if you diy.
 

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Discussion Starter · #17 ·
Anyone able to point me in the direction of a manual for this cm450? I’m going to try and take this guy apart, but would like to have access to a manual I could reference! Thanks.
 

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What did you find clutch side ?

Any large gaps between valve stem top and adjusting screw in rocker arms ?

Don't forget CMSNL views...

Oil filter bolt same size and thread as flywheel removal bolt, peg spanner ideally for clutch nut...

You intend getting an other of these models ... ?
 
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