HELP! 1999 KX 250 popping at high-rpm

[MXYoung]

I have a 1999 KX 250 that cuts out near the top of the RPM range in most gears. I have pulled off the top-end, it is good. I have checked the reeds, - they are good. I have also cleaned the carburetor and no change. I live in So-Cal and use 91 octane gas at 40:1. Nothing has been changed prior to this happening. It just started and has continued even after my checks. Any advice would be appreciated. Thanks.

 

[Glitch]

(Edit: Nevermind)

 

[KX'er]

Sounds like it is running lean or your float level may be too low.

 

[Senior KX Rider]

Mine pops real bad if the main is lean. One size will do it :thumb:

 

[David Trustrum]

If that fails (airleaks etc) try new plug, new spark cap, check electrical connections, kill switch & maybe coil/stator/cdi, but not so likely.

Local supply of gas this time of year may vary?

 

[helio]

Could seems dumb but I have installed a little filter between my petcock and the carb for precaution. Sometime ago it was obstructed by dirt due to bad gas(I never replaced or cleaned this small filter :worship: )...It created a lean condition at wide open as you can imagine.
I thought the worst...a seizure in my bottom or top end but after a good cleaning of that small filter everything fine.

 

[r_rider28]

If suggestions above don't helpcheck your fly wheel as well, if the woodruf key has sheared then your timing is changing which could also cause it to pop at high rpm.
water in fuel could also cause popping.