Last night I put a Lrd Pro 4R full exhasut and dyno jet kit into my raptor. Whata difference. It runs smoothly until all the way at top end. It will idle but back fires when the the throttle is fully open and let go. I used the jets specified in the kit which is a stage two but they didnt even say what size they were. It just went by altitude. I am running with my air box lid on. I really dont know much about jetting. Would gladly appreciate any help

 

If it was mine, i would check for exhaust leaks first. If there are any leaks anywhere in front of the muffler then it will backfire. I've never done any jetting so I can't help you out there.

 

Read this, it should help you out a lot. If you are still having trouble let me know and I will try to help you further on your jetting. CLICK HERE FOR JETTING INFO

 

did you cut the tabs from inside the snorkel?

did you install a pro-fow intake?

what jets are you running? How many turns on the screws?