xr250 backfiring and spitting after air filter clean

[duffbeer911]

Hey all,

Bought a 99 XR250 a month or so ago. Running really well when I got it. Did a few dusty rides and then cleaned the foam air filter, re-oiled it, and now it is backfiring and spitting quite badly on deceleration. I thought maybe I didn't let the foam 100% dry out before oiling so I did the whole process again with extra care ... but it is still happening.

 

What do you suggest I look at next? Thanks for any help

[Oil Baron]

If you remove the filter, does it still backfire?

[Trailryder42]

I think, as BR may be indicating, you're not getting the filter seated properly in the air box and its causing a lean condition.

That or, the filter was way over oiled initially, which the bikes current jetting supports and you didn't oil it as heavy as it was before which is now making the jetting too lean.

So, if you're sure the filter is getting seated properly, try coming out with the fuel screw some to clean up the popping and sputtering on decel. No more than a total of 3 turns out.

Get back to us with results.

[Garon]

I was under the impression that the popping on deceleration was excess gas (possibly indicating a rich condition) getting into the exhaust and combusting.  Am I mistaken in my understanding of 'popping on deceleration' and confusing with engine backfire?

[duffbeer911]

duh .... turns out it was nothing to do with the air filter. On closer inspection one of the nuts connecting the exhaust was coming loose!  ?

 

Tightened it up and running like a dream!

 

thanks for the tips tho