Cam chain

[scotty110788]

The chain keeps coming off the bottom sprocket for some reason even though it's perfectly lined up, what is the sprocket called or whatever it is that it goes round at bottom of the engine?


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[Big Rich]

The crankshaft?

I'm guessing you're doing some work in your engine and that's when the chain is coming off.....not as the engine is running. With the cam shafts removed, you need to hold the cam chain up in your hand while you rotate the crank to the timing mark ( because it can bunch up under the crankshaft). I've never heard of the cam chain sprocket on the crankshaft being "slightly worn" causing the chain to slip off..... but it can be absolutely wrecked from an engine failure.

[scotty110788]

Yea I am, I had a thread going on this issue, got it all set up, turned over mint, put it all back together then bam, it's off again, so if it ain't the crankshaft then I'm back to square one


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[Big Rich]

Just read thru that thread. If you ran rig up a mirror and a flashlight while the head cover is off, you should be able to visually inspect the teeth on the crankshaft sprocket (I don't think anything else would be blocking your view). If the sprocket is worn bad enough to allow the cam chain to slip off, it will be pretty obvious. If the sprocket is in good shape, I'd look at your cam chain tensioner. With the CCT removed, have you tried compressing it by hand?

[scotty110788]

Yea I've tried it with cct removed, no matter what way I try it, everything seems to turn mint then out the blue, it just jams again


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[scotty110788]

Could it be the chain tensioner is not keeping chain tight enough against cams? That it's moving in to much?


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[Big Rich]

Yep, that's what I'm thinking. Excess chain slack is causing the chain to jump loose at the sprockets. That's why I asked if you were able to compress the CCT by hand if it weren't installed.

[sledge]

Sounds like the rear cam chain guide is worn/broken/dislodged 

[scotty110788]

Well I'm going to strip back engine as much as I can and see if I can diagnose problem, spent 8 months getting this far with bike, what's another couple gonna do haha


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[scotty110788]

One of valves had snapped 😩


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[lucas]