ok well im new to the 450r ive had a 300ex an old big red 3-wheeler and a kawi. mojave 25o(big p.o.s. ever) but my questions about the 450r are prettty simple its got a full fmf exhuast and axle,bearings,sprockets and im not sure what else i got it the way it is but when i ride it when i let off the throttle it pops back thru the exuast im just wonderin if thats cheap gas or supposed to be that way or what its the first quad ive had that actually has some real power and upgrades so im just looking for info lol thanks for th help