What causes Decel popping, backfiring??

my 99 yz400f has same issue... I've got a screwdirver to adjust the screw on the bottom of the carb (air mixture screw?), but which way is 2 turns out? clockwise or counter? thanks

my 99 yz400f has same issue... I've got a screwdirver to adjust the screw on the bottom of the carb (air mixture screw?), but which way is 2 turns out? clockwise or counter? thanks

Well I turned a few laps this morning. It was about 85 at 10:00 this morning. Well she ran good the first two or three laps then started to act up again as usual. Dam I am so tired of this stuff. she is backfiring and popping like hell under decel. Studdering and popping a little under hard accel. up hills and out of turns. She will still run good midrange and top but it is just not running like it should. I know if I pull the plug it is going to be black. I will mess with the screw next time I ride but it is set about 1.5 out and everything else is stock except BK mod. I wish I could just ship out the bike to one of you jetting gurus so you could fix it. A case of beer would be included of course!! LOL I know that everyone is tired of hearing the same ole thing out of me but I am stumped. Me and my mechanic are gonna work on it next week. In the mean time I am gonna order a 38 pilot and a 165 main. Those are about the only two jets I dont have. I think the main is fine at 162 though but I might need to do something with the pilot. I give up, anyone want a 426? Just kidding, Frank :)

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