[Jessy]

Hey guys I'm new to forums. I've read alot on here but just cant seem to find the specific one. I have a 2001 honda 400ex I put a 440 bore kit on with a lexx exhaust k&n filter and stock carburetor. Just reacently installed a stage 1 hot cam and It backfires at high rpms. What do you guys think the cause is for that. I know my carb has a 155 jet in it. I do have a 175 jet laying around if I should try that.

 

[SlammedRanger]

155 isnt even in the relm of what your quad needs. Heck the 175 probably wont even do it. That is if your talking about keihin jets. If your using dyno jets thats on a whole different scale. I would be starting with somewhere around a 185-190. And i would be going to a 45 and possibly a 48 pilot jet. Welcome to the forums.

 

[atvrider13]

I agree with slammed. Up your main jet for sure

 

[TRX2fiveO]

Welcome to the forums. . . Stock carb.... 440.... exhaust.... 180 main 45 slow 2 1/2 from seated on the fuel screw should get you within the testing range to run a valid plug chop.