I have a 80" evo and it likes to back fire after decell when taking off and somtimes random.... Its got pipes now and been to the harley dealer and been jetted main from 160 to 170 and slow speed from 42 to 46 and it seems worse then before ??? And the plugs don't look to bad !! Any thing common to cause this ?? As a intake gasket or intake??

Thanks guys you been a great help in my project this far !!

 

Id bump the main up to a 175 or 180. Decel Pop = lean.

 

Check exhaust for leaks too

 

I'm guessing the dealer didnt adjust the air mixture screw.Its sealed at the factory.I had mine rejetted after I put new slip-ons on it and the mechanic said it was against the law to change the mixture.It backfired like all hell till I removed the cap that seals the mixture screw and opened it up some.

 

What everyone else has said and/or possible timing issue. Is your VOS working? Did it start after the pipes or did it do it before the pipes too?

 

Popping after decel is common with a lean idle mixture.
when you let go of the throttle the motor is still pulling air through but not enough fuel since you are now on the low speed mix (pilot jet or idle jet as its often called),so you end up with a lean mix when you crack the throttle again.
If it was an issue of my fuel injection id be either looking for an exhaust leak or adjusting my fuel map at the 0-5 % throttle position


Could be any ,or a combo of these things.

-accel pump not spraying correctly
-pilot jet too small
-pilot jet plugged
-float incorrectly adjusted
-mixture screw incorrectly adjusted
-intake leak
-exhaust leak

 

+1 the pilot jet seems good, but id up the main
And turn the mix screw out a half turn out. It shudld
Run better as long as there's no leaks.

 

You can cause it to pop with the throttle. Both my bikes are tuned rich but I can decel pop both of them.

 

I had the same problem when I got me evo. I rejetted and adjusted the mixture and problem is gone. That being said, I still get 1 backfire through the pipes when starting the bike after it's been ridden and is warm. Still trying to track that one down.

 

Install new plugs and wires.