[BUCK21]

I haave a 2008 450X that I have had for about a year or so. I added a FMFPowercore 4 pipe which made a huge difference in the performance. I seem to be getting alot of backfires now and friends have suggested changing the jetting might fix the problem. My friend has an '05 and the same pipe. He changed out the jetting to a 170 and a 48 main. I am wondering if this jetting would be the optimal way for me to go. Any help or suggestions?

[Charlie C]

Sounds like you're dealing with a mild lean condition. Before jumping into the carb and changing the jetting, try to adjust the air/fuel mixture screw on the bottom of the carb. You will have to turn the screw counter clockwise, but be carefull as to how far you back it out. Anything more than 3 turns out from seated, you take a risk of the screw vibrating out.