I have an ata250d Tao that I just replaced the back sprocket and chain on, because it looked as if the sprocket was bent. After getting it off the chain and sprocket really don't look bad but put the new ones on anyway. I got it nice and tight, drove it for 10 minutes or so and brought it back in a retightened. Drove it again and it's falling off like crazy, though it is still tight when I put it back on. Any ideas? There appears to be a slight bend on the chain near front sprocket.

/e I got it straightened up and tightened it a bit more. It's still coming off, and there is no play in the swing arm. I'm real lost.

 

Looks like the rear is slightly off center. Also did you check and make sure the chain is the right pitch? If is the wrong pitch the chain will look like it fits but under load fall off.

 

No idea what pitch means on a chain. I just ordered an oem (supposedly) chain.

 

Look on the side of the chain and sprocket. u should find a 3 digit number. they need to match between all 3 pcs

 

So that's what the 420 and 428 is then. Gotcha. The chain says 428, but I can't find any numbers on the sprockets. Front sprocket says SLAN, but no numbers.

https://taotaopartsdirect.myshopify..../rear-sprocket

That's where I got the chain and sprocket, and I assume they would only sell matching pieces since there's only one option for each. I did not replace my front sprocket, and the one they sell on that site is a 15 vs my 13. Maybe it's a different pitch too. I have my chain nice and straight now, so I don't know what else to blame it on lol. Or another option could just be that it's a crappy chain and keeps stretching any time it's in a bind? I can shift through all the gears, but if I ever put a real load on it it slips.

/edit I just looked at my old chain and it was 428 too so my sprocket has to be as well.

 

It looks like the engine and rear sprockets are not lined up so, is the engine tight in the frame. Is the rear sprocket on right, (some can be fitted to the left or right of the hub.) The chain should not be tight, Honda recommend 1" play (0.5" up 0.5" down) on 90s This should be checked with the normal rider's weight on the seat, and spin the chain a bit and re-check, as you do get tight and slack spots.

 

Yeah I messed with it a lot after that picture and got it somewhat straight. It ended up being the swing arm bushings! Couldn't really tell until I got it apart. Thanks!