Reread the dyno jet instructions. The recommendation is to duct tape off the airbox opening, use more tape to richen up the jetting.

The trouble shooting guide also tells if you have decel backfiring to open up the fuel mixture screw 1/4 turn at a time until it goes away. Good reason for the kouba screw...

 

anybody able to 100% get rid of decel backfire?...tried even micro-adjustments, but had no luck....if i go from full-throttle instantly to zero throttle...it'll pop pop pop....if i roll off the throttle smoothly, i get no pop...my moto runs strong and sounds great....but, quick slowdowns or extreme downshift...i get the decel pops....is that a problem?...

 

I was able to get rid of the decel popping. Some insist that a 40 pilot is to big, but I have read that afew around here do run one, mine ran fine with it. I ran the dynojet needle 3rd clip. One small improvement was to grind the weld bead in the header flange to improve the flow in that area.

https://www.kawasakiforums.com/forum...erbomb-006-jpg

FMF powerbomb in the center with two oem headers

 

Since I rejetted I've had to do this as well. My screw is 2 1/2 turns out & no snorkle on the airbox lid. When running stock jets, warm starts were fine; no throttle needed.

 

After several days of riding I'm happy to report turning the screw in ever so slightly was the trick. It's firing up like new when cold and hot without the chock. The popping increased on decel but only minimally. I would say I'm probably around 3 1/4 turns out.

 

My bike is jetted as the per the dynojet stage 2 instructions and it has no popping on decel, none at all. Just lucky I guess as I am a medicore mechanic at best.