I recently put an hmf pipe, k&n filter and 142 main jet in my vinson. The piolet screw is set a 2 1/2 turns, but it's not running right. It was fine when i first put everythig in but now it's not. Top end power is bad, and acceleration is very flat. The engine also pops and backfires on deceleration and stalls sometimes. No matter what i do to the piolet screw it will not stop backfiring. I Pulled the plug today and it's silver. I assume it's running lean, but why has it changed since i installed everything? What should i do to fix it? Just put in a bigger jet? I'm just getting really pissed off and i'm about ready to get out the sledge hammer and fix it for good!!!

 

go for it