[Scooter Roberts]

I recently got a rex 450 s from a friend. When I got the bike it was smoking and wouldn't run good. Backfiring and seemed to be choking out. I've had new rings, carburetor, and intake manifold. I can get it set to a good idle, but when you start giving it fuel it acts like it's choking out and backfiring. Has a rattle in the motor so adjust the valves to .006. Still have the rattle.

 

[shadetree]

when you installed new rings, did you bother to check the connecting rod for any play ?, is carb oem ?, or some china junk from ebay/amazon ?. did you check the cylinder for ring clearance to cylinder ?. did you set valves on exhaust stroke or compression stroke ?, did you follow instructions from the service manual ??.