I am new to the sport and bought a yz450f 2006. It backfires whenever I let off the throttle. Not a horrible amount maybe four or five pops when coming down from 3/4 throttle. Is this something that is bad for the bike or performance of it. I read the rejetting section and it would seem that If I do need to do this I would go to a 45 jet. Or should I just try to turn the mix screw out some. Thanks for the help.