125-200cc 2009 WR125 Extreme lean condition

Bike runs fine when it is cold, then after 3-5 minutes of warm up, it starts having an extreme hanging idle. If you continue to ride it (like I did since I was a long ways from the house), it got hot enough to diesel on. The kill switch wouldn't kill it, and I had to stop it in gear with the brakes.

So, I don't believe the carb is the issue. I set the float a little higher to make sure it wasn't running out of fuel. I richened the rod to the point it was really loading up. I checked the air boots on the carb to make sure they are tight. Any other ideas?

When you first start up the bike before the high idle starts,spray the intake boot area,reed/intake mounting area with carb cleaner.Any air leaks will be detected by a erratic idle once you hit the leak with the cleaner.

No changes in idle after you spray would point me torwards the carb.
To me it sounds like you have a leak near the intake area that happens when the bike warms up?

That sounds bad. If you adjusted your rod make sure its facing forward and sits flush. Other than that it has to be some crazy leak, crank seals, or reed block

Did you ever figure this out?! I developed the same symptoms not quite as extrene but also runs fine when cold but gets upset once hot. Surging, hanging idle erractic and such.

Maybe check the crank seal on the flywheel side. It may be leaking. While the flywheel would spin, air would push in like a turbine.

I've also seen similar ( but bizzare) symptoms from a severely clogged expansion chamber. But I think that was a rare occasion.

Also, check/adjust air screw and check the seal on top of the carb that holds the slide down.

I very much think its something i caused. I removed the carb to test on another bike. It ran flawless. Put it back on originial bike which ran flawless before, now developed this goofy problem. Checked and rechecked the boots, the rod (lectron) the gaskets the every thing and cant figure she out.

It was within 10 minutes of the first ride it happened after swapping it back. It started first kick went together smoothly only sign something was off was i had to adjust the idle a bit from the previous setting but chalked that up to reassembly or who knows what. All settings are unchanged except now i richened the rod a half turn because this is a lean symptom and a half turn wouldnt drastically change anything.


Very much want this back to nornal so i can ride it and not my back up beater old Yamaha.

So u did re-adjust the air screw? They can vibrate loose. Especially when playing around removing and installing the carb repeatedly. Hopefully your intake boot(s) didn't crack.

Im thinking it has to be an intake leak. Going to get starting fluid and spray the boots down.

hes using a lectron, there is no airscrew. just an idle screw and power jet screw.

Had this problem, chased it for months... Turned out to be a gasket leak, can't remember which side though.

Blake, gasket leak in the lectron or an intake boot. Come on think buddy!

on one of the side cases... cant remember if it was clutch side, but I think it was.... When I pulled the case cover off, I could see where the gasket had a defect when installed, but held up for years, until it finally gave way...

It started great, and would run flawlessly for about 5 minutes, Then it stared to produce super lean symptoms. After it sat and cooled down, it would run fine again for 5 minutes... I tried messing with the lectron to no end, I tried spraying the boot and reed cage with starter fluid, nothing.... Once I replaced that bad gasket, it ran great... Best of luck. Keep us updated!

Sounds good, im not sure i understand the workings of a 2 stroke well enough. Never had a bottom end apart. i dont understand case gasket to be honest.

Im going to exhaust my other options, reeds, 100% verify not intake leak, easier simple stuff, im still leaning towards its something i did since i removed and reinstalled the carb. I just cant see what it is! I really want it back!!

Not going to be any other gasket other than reed cage on 2stroke.
If you replaced magneto/stator gasket and that cures it then its your seal!
there are seals either side of crankshaft one on magneto, air tight
One on clutch side, oil tight if these leak they can cause hard starting/ lean running air side
Rich running plumes of smoke oil side.

You get them just from taking off the case covers? Or do you need to split the cases?

The seals for crank?
You need clutch side off and to pull a few gears off but dont think thats the one. The flywheel and stator plate need to be removed and its in a recess in the case there either way no cases shouldnt need to be split, but may be speaking out of tirn as i dont own 125. Check halls for manual should have parts diagram usually that shows you which way seals n bearings are put in from.

I popped the ignition side cover off and there is a small amount of grease/oil/ slimy crud along the bottom of the case. Its far from like leaking oil or something but is also not bone dry by any means.

I tried spraying starting fluid all over the place With zero improvements.

Thinking it may be that crank seal ignition side as suggested,