Hi. I have a 2000 Recon. Bought it as the guy was hard for cash around tax time. I knew I would need to put some work into it. I stripped it down to the frame, changed oil, cleaned out air filter, air box, etc...It likely never had been cleaned or washed, ever. The oil looked horrid.

Okay, when the bike starts although smokes and has a solid knock. Not pinging, a knock. It runs solid though. Occasionally it backfires at low throttle. I am thinking this guy got some dirt / water in the engine and damaged the top end. Any ideas?

I do not mind the smoke as it is minimal. However, the knock and backfire have me concerned.

Josh

 

the backfiring sounds like a rich mixture. The fuel collects in the exhaust and when enough gets there it ignites from the heat. If the machine is running rich, it's likely the cylinder was washed of its oil and the rings scored the cylinder.

backfiring could also be lean, but it's usually on a hard deceleration when that would happen.
take the carb apart and clean it, then see how it goes. good luck