Maybe someone can offer some suggestions as to what might be the problem. I just installed the full DMC Alien dual exhaust system, and jetted the carbs with a dynojet kit. It fires right up, idles nice, responds real nice to throttle.. but when i rev high and let off the throttle, i get a popping backfire.. pretty annoying! I havent really checked anything out yet. I followed the instructions in the kit, put a 146 jet in the left carb and a 148 in the right because I'm at about 1500ft above sea level. Screwed both the fuel mixture screws all the way in, then backed both out 3 turns. Put everything back on the quad, and it fired right up, idled well.. just got the backfire issue to contend with.

Any help would be appreciated!

Thanks

 

You are probably a little lean. Check your plug.

~HoundDog

 

Welcome to the forums!

You sound lean on your idle mixture, turn the screw out a bit more

 

after 3 turns out on the pilots, I would suggest going with bigger pilot jets.

 

Thanks for the welcome! I will try that out and see. Thanks

 

Why's that?

 

your maxing out the pilots, so if you go with bigger ones, you will only turn them out 2 turns or so.

 

I have A Full DMC Alien on my 04 Raptor. Try running 27.5 pilots air screws 3 turns out (left carb) 3 and 1/2 (right carb) and 155 160 mains with no airbox lid or one thats drilled out really good. thats a good performance enhancer, but the poping is just your pilot jets run 25's or 27.5's if it persists. (same size pilot in both carbs)

 

I mean 150, 155. 155, 160 is with a k&n with no lid and 160, 165 is dual k&n with no airbox (thats what i got).