Hey guys, I just bought my first dirt bike about 2 months ago. 2002 yz426f w/ a very high flowing header and very old school pro circut race pipe. I think it still have the stock jetting because it back fires and pops quite a bit on deceleration. Right when I got the bike I put a fmf power bomb header and fmf q4 pipe on it. It still backfires and pops on decel a lot so I was hoping to get some help with the jetting. This is the first carbed anything I have ever owned so I don't know a thing about them. Can someone walk me through what exactly I need and how much it should cost? Secondly, Up until recently the idle screw has worked just fine, but now my idle is pretty low and turning the screw has no effect on it... Any ideas on what is wrong? All in all this bike is awesome though and Im having a blast with it!