I have been reading past posts and have learned a lot! I bought a 07 yz450 a month ago. I love it. The question i have is that it backfires quite a bit at decel. How much is acceptable. I also dont get it started when cold until after about four kicks. Idle is steady. every thing is stock. UNI filter(clean), 160main (stock),1500-3500 altitude(eastern oregon), 50-100 temp. air screw set at 1 3/4-2 turns. any suggestions much appreciated.