I just had the dealer and Yamaha let me take a carb of another new bike to put in mine, (the usual popping on decel) Rode it yesterday at the track, the bike actually runs great, fairly minimal pooping on the last bit of rpm's. I had another guy with an 06 and an expert rider ride it and he thought it was fine, the little bit of popping is OK. So this morning I put in a 168 MJ (we have a 48 PJ, stock needle 5th clip, 3 turns out FS and had a 165 MJ yesterday) and it pops pretty bad after riding it for 5 minutes. So obviously it's 15 degrees cooler this morning, maybe 60-65 and yesterday it was maybe 75-80. I sealed the exhaust, checked the hot start for slack, rejetted, reneedled several times, NEW carb, so the question is what is it about the YZ that requires this, the 06 CRF I had didn't do this at all, never touched it, no popping ever. The carbs are different on these two bikes, both FCR's but different. At the lowest RPM's on decel it seems the motor simply can't pull in the fuel it needs, or the air it needs to pull the fuel. Any thoughts?