Chain slapping jumping under load.

[Ariel Red Hunter]

Originally Posted by Kivi

I found out that the problem greatly disappears if the chain is adjusted to have just a small slack - 10-15mm while unloaded. But, when set this way, chain streches after every ride! Because chain slack need to be about 6cm unloaded, so that as suspension compresses, at the max compression slack to be 1cm.
So, this looks like a bad design. Badly designed Yamaha cloned frame for this Honda cloned engine. Unfinished product. Poor engineering (if any).
But, I think weather to try to fix this or not. To move the engine mounts, or to move the swing arm shaft location. Also rear suspension need to go to trash and fabricate new.
IF you have any thoughts......tomorrow I will put a photo with sprocket cover removed.

Yeah, they call that causing a worse problem while fixing the first problem. I have been thinking about your problem for several days. I would start by checking the rear sprocket/front sprocket alignment. If that is ok, the next thing I would do is take the chain off and check alignment of the sprockes again at full droop and full compression. Check that the swing-arm bushings are not allowing the rear wheel to go out of line. If that doesn't do it, it's more serious - a slightly bent frame or swing-arm...ARH