I am trying to mess with the jetting and what-not on my dad's XR so I can use it tomorrow for my motorcycle license test. It's being a pain in the butt, so I figured I'd ask you all if you had any insight into the situation. Especially you guys with the BRP (big red pig). First of all, I uncorked it for him, so it has the HRC exhaust tip and the bigger intake manifold, and put in a 68s pilot and a 175 main. I also pulled out the snorkel and the plastic baffle in the airbox It runs fine at high rpm, but when backing off, it was backfiring. Sometimes when letting off and coming to a stop, it dies. I have been playing with the fuel screw (on the right side of the carb) and the idle screw, cause I figure it's only doing weird things at low throttle positions. Then, to cure the backfiring, I lowered the float level so gas wouldn't pour back into the airbox. We started it up, and it hasn't wanted to backfire, but it won't idle cleanly. If you rev it up, it won't idle down for about 5 or 10 seconds. What's up with that? It seems like I fixed one thing, and messed up another. I just don't get what could make the thing not idle down for that amount of time. Any help you can give today would be appreciated cause I gotta ride the damn thing tomorrow to get my license! I am used to working on 2-strokes, so I'm only learning this XR 650 stuff. Could this be something simple that I just overlooked, or should I play with different jetting.