It seems like my KLX250 is backfiring if I let off throttle suddenly at high rpm. It idles and starts well and seems to run find otherwise. Is this an issue or do these bikes tend to do that?
The bike was rejetted by the previous owner but he didn't remember what the setup was. It has a FMF Q4 exhaust and the airbox lid has been removed, all by previous owner at the time of the rejet.

 

Is it backfiring or just popping on decel?

 

Mine was decel popping after high rpm runs, a little more fuel with the A/F screw fixed it.
Decel pop is not as loud as a backfire, which can be loud like a gunshot.

 

Classic air leak at the exhaust header... try tightening the nuts on the header clamps.

 

From those descriptions it is more of a popping than a backfire. I tightened the bolts where the header starts (those sure are nice to get to) and the clamp at the exhaust and header. Ill see if that helps.
It wasn't a big deal, but I wasn't sure if it was a problem with the bike or normal.

 

Decel popping is all in jetting, my KLR does it, my KLX does it, my truck does it which with the flowmaster makes a nice raspy noise yea im a gearhead.

I did see a KLX in NJ with a HMF slip on jetted so rich that when it decel popped it shot flames out of the back like a foot. Pretty sweet, but a tad rich, lol

 

i like this quote... "Any 4 stroke engine--even those that are flawlessly tuned will pop on decel. It is harmless, but can be annoying--granted. However, I would never alter the jetting of an otherwise performing motorcycle to get rid of it. Go by the seat of your pants and the color of your spark plug rather than the popping as an indication of the jetting of your scoot!"....from Deceleration Popping explained

 

TRUE "backfiring" is a bad thing. AZR, did your header bolt tweek help?

 

Yes, seems to have done the trick. I haven't noticed it since.

 

your welcome