Motorcycle Repair: 07 crf450r, air fuel mixture, 07 crf450r

Question
Gary,

I recently got this bike and it was running great, aside from the difficulty starting when hot. I purchased the boyesen QuickStart3 and installed it today. This made a world of difference for starting the bike and its much easier now, hot or cold. The problem is the loud, excessive backfire in deceleration now, which was not an issue before. I've tried making minor adjustments to leak jet(adjustable w/qs3), idle, air/fuel mixture.. I can't figure it out. Any ideas? Any knowledge on this subject will help. Thanks.

Answer
Brian, My son had this same bike. His however was more noticable with the after matket FMF pipe. He did not have the hot start set up but it may be an annoying problem thats the "nature of the beast" thing. Try checking the cylinder to pipe seal as they can suck air and do similar things.