just had my exhaust done on my P700. I had 5 1/2 inch holes drilled with the end also opened. Now the bike backfires when coming off of wide open throttle. I took it back and they said they also put a hole down the middle of the muffler. Does this sound correct? If so, how do I get rid of the backfiring.
This is the only mod I have done. I tried bigger main jets but it made it worse.

 

turn the air correctors out 1/4 turn. Mine did it too. Just STAY on the gas! HA!
What mains did you try?

 

You might also try turning the mixture screws 1/4 turn past the fastest idle. You might find that your V needs one cyl richer than the other, and maybe not. If you adjust the screws rather than just turn them, you might get bvetter results.

FYI, backfire at decel is usually idle mixture, but could also be valve adjust or exhaust pipe leaks.

 

I have found on other machines if the idle or say the slide is to low the motor wants more air. Up the idle a tad and see.

 

Just so you know the air mixture screws are, the brass ones set back in the carbs. I would turn then all the way in, clock wise. Turn then counter clock 21/2 complete turns. Ride the quad a few time then keep turnning out a 1/2 turn until it stops back firing. This should work? You might even wanna change your jetting? I dont know the drilled holes in the stock muffler mod? But Anytime you do an exhaust mod you should rejet? I switch Mufflers from a HMF to Stock Pipe from time to time, running 142/145 The Stock size I beleave was 138/140? Going back to stock all I do is turn the mixture screw out twice verses 31/2 turns out on the HMF with no problems! I also have a DG snorkel and a TPI Valve on the top of the air box. You do wanna get some more air in the box! ~Coop

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has anybody not had to adjust the mixture screws after they did the NAPA hose, filter any exhaust mods?