Topic: Clunk or thud sound

[my78k]

I posted this on the cbr forum that I hang out on occasionally but their tech section is weak by comparison to the ones on here so figured I would take a stab at it here too...this is my daily rider and just started acting up...

98 CBR600 F3...we all have the same usual clunk when we drop it into first gear...I have just recently though picked up a new clunk.

When it is in first and I let the clutch out and start to roll about a few feet I hear a clunk sound...if I continue to let it roll at around the same speed I hear it again. If I accelerate and get it up into second etc I don't hear it (though it may be masked by the sound of the engine).

This just started happening this weekend on my ride home from the cottage...was fine at first but after 100kms or so of hwy riding I pulled onto the back roads to avoid the long weekend traffic.

Any thoughts as to what it might be? Chain slap if it is too loose? The rear sprocket looks a bit worn but nothing too bad...haven't pulled it apart to see the front...

Any thoughts appreciated!

Dennis

[KB02]

I get a fairly similar clunk on my Ducati. MY chain is tightened to within spec, but the sprockets are shot. The rear is a little bad, but the front is horrible.

I'd say it is inspection time. Check out that front sprocket to either confirm or dismiss it as the culprit.

[my78k]

Thanks! That is sort of wat I was afraid of...I don't have the cash right now and was hoping to wait until winter to tackle it

I'll give it a look over this weekend...

Thanks again,
Dennis

[HITMAN]

I am having the same issues with one of my bikes, letting out the clutch and 'clunk'.  I took the front sprocket cover off and watched it while I let out the clutch with many variations of adjustment on the chain, and you could see the front sprocket jump or shift (NOT the chain jumping teeth as I initially expected to see).  The conclusion with mine is toasted chain and sporcket, too much thrust for the sprocket shim and finally a slightly sloppy output shaft bearing.  Needless to say this bike is getting parked in favor of finishing the cafe.

Hope this helps

[wadarush]

I have no clue if this vintage technology is still in use on a bike this new but does it have the large busing that transfers the drive chain energy to the rear wheel.  If that is worn out I'm sure it could make quite a racket!