Intermittent sputtering, goes away after restart?

Hey guys.

I'm trying to trouble-shoot a problem with my 2007 WR250. It's pretty much always been an issue, but more frequent and irritating lately. Wondering what you think it may be.

Bike runs awesome 1/2 the time. The issue only happens after the bike has been running for about 20 seconds or so. On a fresh start, I can rev it too the moon, whack the throttle even under load and it launches nice and crisp with little to no bog and it revs all the way up. After 20 seconds or so it starts sputtering or losing power about 1/3rd to 1/2 way through the throttle. Low throttle seems fine. Issue doesn't go away unless I turn off the bike, but then it comes right back.

At a race the other day I was having the problem during practice, first moto was great with no issue and then the 2nd moto was terrible again. I end up having to really lug it around the track/hills at the bottom of the throttle.

Any ideas? I've tried flushing the fuel, draining the tank, cleaning the carb, all to no avail. Is the main jet so picky that it's possibly I'm barely off and it runs great sometimes and crappy others? I'm not much of a jetting expert.

Bike Setup: YZ timing, mega-bomb/Q4 exhaust, airbox opened up, boysen quickshot, adjustable fuel screw, GYTR needle.

Altitude: 4000-6000ft, 170 main, 45 pilot, clip 3rd down, #50 leak (1 1/8 turns out), fuel screw 2 turns out.

Thanks for any ideas or suggestions!

May or may not fix your problem but try riding it with the TPS disconnected. I had a similar scenario

Also, try a new spark plug.

Well, looks like it was due to my hot-start cable being unscrewed! :thumbsup:

This was found after changing all the jets numerous times to no avail. Crazy.

Thanks for the help though.

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