Need some help and thought I would try you guys. Right now I run a HMF slip on open air box w/ k&N and proflow adapter, I am concerned with backfire. I am at a 170 jet with the air/fuel screw out 2 1/2 turns (maybe) Called the dealer and said I may be running rich. They suggested going to 165 jet. Have the stock piolt in there as well. I have carbon or black soot on the exhaust tip. There is no sputtering or backfire when accelerating just off throttle popping sometimes with a flame out the backWhat is going on? Thanks for the help

 

the black carbon and flame out the exhaust is a def sign of too rich. excess fuel goes threw the combustion chamber and ends up in the exhaust. try a smaller main or playing with the needle settings to get it straightened out.

 

What bike are u talking about? I c yfz in your nick name. Also are you running dynojets or mikuni's?

 

It is an Yamaha 450 2005. Keihin jet are what is being used

 

Got the 165 jet on and some mixture screw tampering got rid of most of the backfire. I am going to jump up to a 45 on the pilot so hopefully that will take care of the jetting