Hi, so I've got a ATA250-D that's been brought in to have the carb cleaned. I work at a small engine shop where 90% of what I do is lawn mowers and snow blowers, so I don't have much experience with ATVs. Anyways, I drilled out the original snap-off screws, cleaned the carb, got it idling fine, went to take it out for a test-drive, and the chain fell off the rear sprocket. I put the chain back on, was a little more gentle with the clutch this time, and the chain came off a few feet after I took off. So I looked down, and found this stud sticking out



I'm assuming there's supposed to be either a tensioner or roller on this stud. There's also no guard on the rear sprocket. Where can I get another one of whatever's supposed to be on the stud, and a guard for the rear?

 

I have found many parts on E-bay very cheap, This is a roller type tensioner, I have herd of other people using a sprocket on here, this is what I am leaning towards but with the odd size chain is not so easy to shop for..