Help , New sprocket

[Whytey]

Just put a 15 th on my bike down from a 16 th and tightened it up and it starts banging and making all sorts of shitty noises . the bottom of the chain sort of rises and falls so i loosened it off again and moved it a tooth on the bottom off the rear sprocket but to no avail .
the chain and sprockets are in really good nick by the way .
Any ideas ?

[Ixion]

I'd double check that the sprocket is properly mounted and the chain run correct. Assuming your chain really is in good nick, because a badly worn chain will do just what you describe.

[Whytey]

No it does,nt seem to loosen or tighten the rears nice and straight . I jues went and put the old one back on and it done the same just a little less . could it be that ive got it up on the stand and nothing to put load on the chain ?

[Tony.OK]

No it does,nt seem to loosen or tighten the rears nice and straight . I jues went and put the old one back on and it done the same just a little less . could it be that ive got it up on the stand and nothing to put load on the chain ?

Yeah it could be no load,the wheel will try to spin faster than the motor,it may be slapping on the top side going into the front sprocket cover,set the correct sag and try a road test.

[yod]

yeah, mine was the same on the paddock stand when i replaced the chain and sprockets, i think you're right, no load, it should be fine on the road, i had no probs

[F5 Dave]

The chain always finds it a drag going around the front smaller sprocket. This is why they generally wear the quickest. If the chain has to make a tighter bend then the worse it is. If there are any tight spots this will be amplified as the chain is worn to bend around a 16 & you are asking it to go smaller + it has worn the sprocket to match. Depends how bad it is but might be a chain issue.

I prefer to increase the rear ~3 rather than decrease the front if can be avoided, of course this is more expensive & likely stock chain too short.