hanging throttle

hey guys,

I have a 2001 WR 426 and its having a wierd throttle problem. It seems to hang just above idle, but not like its running lean where it revs high and then within a few seconds it comes back down. When its not hanging and idleing correctly, the bike revs low enough where it stalls. It intermittantly runs like you have a govenor on where its keeping the revs up just enough to make it tough to slow down. When the revs are up, the bike will chug along like yo have the gas on just a little bit. Other than that I'm revving it up all the time to keep it from stalling. Its a hard problem to explain, but I'm always chasing the idle. Sometimes I'm reving it up to keep it from stalling and other times I'm trying to make it go down to a lower idle, and adjusting the idle screw doesnt fix the problem because the bike is always switching between the two idling revs. Any hints?!??? I'm fighting between stalling and taking off, and the bike is controlling me!

Remove and thoroughly inspect the throttle slide plate. Many have experienced cracked slides and the symptoms you describe are what happens when it cracks. Any hairline cracks in the slide plate will cause this and will eventually lead to the thing coming apart and parts of it getting sucked into the motor.

Yikes! Parts into the motor are not fun! I recently had the slide plate out, and it looked to be ok, although it was the first time I saw the slide plate out. (I'm assuming that thats the grey car in the top of the carb that holds the needle, right?) Two days ago I dropped the carb off at a local shop, and they didn't notice anything broken/out of place/dirty/wrong. I got it back today, but the problem is still here. Could it be anything outside of the carb? Could it be a setting? I have the insert out and the timing advanced, but I'm running with the lid on because I thought it could have been a lean problem at first. Thanks for the input Rich and anyone else!

Check to make sure the slide plate is in correctly. Its the thin plate on the engine side of the slide. It should be installed with the flat side down. It is very easy to put it in with the round side down resulting in performance that fits the symptoms you are describing.

Thanks!

With the wrong side down wouldn't the idle be constantly high instead of jumping around? It seems to rev high, then normal, then jump to high again. Also, it never seems to go to the lower idle after revvingthe throttle/riding. It alsways reverts to the higher idle after the throttle is closed. :thumbsup:

You may have an air leak. Possibly in the boot between the carb. and the motor. When you are idling spray some WD-40 around the carb. and motor. If you hear a change in RPM you most likely have an air leak. Just hope it is not the head gasket. :thumbsup: Also, if you have hand-guards they sometime cause the throttle to stick especially after one takes a fall. :awww:

Thanks!

With the wrong side down wouldn't the idle be constantly high instead of jumping around? It seems to rev high, then normal, then jump to high again. Also, it never seems to go to the lower idle after revvingthe throttle/riding. It alsways reverts to the higher idle after the throttle is closed. :thumbsup:

Actually no. It will kind of drift around and when you let off the throttle it will kind of hang for awhile. Very weird.

I tried the WD-40 trick, no change in RPM. The boots seem pretty tight. I may have the slide plate in upside down, like PDB said... I'll check tonight. It doesn't seem to be a sticky throttle. Its not in the grip or the cables or the plate where the cables attach to the carb. (nothing appears to be hanging up.) Any other places the air could be creeping through?

Check the slide plate very carefully. I had to use a magnifying glass to see the cracks in mine. They start to crack on the bottom part of the circular indentation. Gently wiggle the sides a bit to see if a crack opens up. I just replaced mine and they're a tad pricy, $148CDN. If you removed the rubber O ring on the back, make sure you put it back with the right side up. throttle_plate_1.jpg

Thanks PBDBLUE!!!!The slide plate was upside down! :thumbsup: Works alot better now, although there's still the original surging problem at constant throttle that started all this. I saw some other posts that talked about needle position, although when I changed the needle position, the bike would only run with the hot start on. :awww:

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