2011 kx250f idle

First of all, I'm new to the forum so I apologize if this thread would be better placed in another category.

Not too long ago, I picked up a 2011 kx250f. Factory kawi head, weisco piston, Yoshi exhaust... all that good stuff. The owner liked the idle as low as it could go for whatever reason (he qualified for Loretta's A class so I guess whatever works, right? Lol). The bike seemed mechanically sound despite the fact that it kept dying on me. I figured I just needed some time to adjust the idle the way I liked it considering it ran fine when he took it for a spin. Now that I'm sitting down with it, I'm a little stumped. The idle has to be pretty high for the bike not to die when you hit the clutch. Higher than I'd like. The bike also dies really quickly when the idle goes about a step below that previous point (still higher than I'd like). What do you guys think the problem is? I've had a friend of mine suggest an air leak.

Also, the bike is nearly impossible to start even though I've checked and made sure the valves are in check.


Is that an OEM spec piston or high compression? Air leak could be. Check the boot from throttle body to the head. Should be no cracks and the clamp should be tight but not too tight. You can spray a little carb cleaner in the area while its idling to check for an air leak. Revs will climb fast if there is. Easy enough to check the plug, too, and the air filter. Next steps are the familiar compression check, double check timing, clean the injector, clean the gas tank, consider the fuel pump, leak down test of the valves, maybe check and adjust the TPS. Did I hear you correctly that the thing stalls when you pull the clutch in? That's strange. Any othe symptoms? Backfire, bog, etc? Let us know.

Its high compression. I'll get on the list to see if I can nail the problem. Thanks for the input. No other real abnormal symptoms. No matter if its hot or cold though, it always acts like its flooded when I try to start it. Its actually easier to start cold than hot for this reason.

What's the easiest way to upload video to this forum? I'll post a quick vid of it just so you guys can see what's really going on.

Post to YouTube probably

What's the easiest way to upload video to this forum? I'll post a quick vid of it just so you guys can see what's really going on.

Starting to really like photobucket.com. Easy sign up, then drag/drop video from desktop into photobucket. Once vid is in photobucket, you click on a link to the right (bottom one) and it copies automatically. Then you paste here. Easy.

I think your problem is the high comp piston. You may need race fuel or a 50:50 mix, and the gas has to be fresh. I'm sure one of the guys who knows about the high comp thing will be more help. I know just enough to know I don't know much at all about high comp pistons.

Your friend suggesting looking for an air leak is a good idea. You also have to look at possible partially clogged injector.

lastly, check the TPS for correct voltage. Those go bad quite a bit.

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