Back fire

[quadrider11]

A friend of mine has a 02' Raptor. It has DMC allien exhuast, K&N fliter, & Jet kit but it back fires when its cold. Any advice?

Thanks

[450RGNCC]

my 450r sometimes backfires a little bit when it is cold, but once it is fully warmed up, it completely stops.

[zeppelin]

go down to the bottom and read the part about the fuel/air screw ;)
http://www.exriders.com/vbb/showthread.php?s=&threadid=221872