Strange Gasgas Problem

[hgas]

hi all ,would appreciate any advice with a strange problem i keep having with my 09 250 pro .

when im out riding the bike is fine runs fine ticks over fine etc but every now and again the throttle will stick wide open and revs to the moon on its own ,i either have to kill it or it shuts off and goes back to normal again.throttle cable is fine the base gasket hasnt long been done and have fitted new reeds which i thort would cure it but still it happens ?!?.if any one has any ideas id be very grateful

cheers =)

[1956mga]

hgas,

Might be too simple but If there is an air leak between your carb and the head your bike will rev like that, (happens on my 300 pro) you might have a small crack in the rubber around the clamping area for the carb. A real easy fix ( so fingers crossed that's all it is),

best of luck,

[jse]

hi all ,would appreciate any advice with a strange problem i keep having with my 09 250 pro .

when im out riding the bike is fine runs fine ticks over fine etc but every now and again the throttle will stick wide open and revs to the moon on its own ,i either have to kill it or it shuts off and goes back to normal again.throttle cable is fine the base gasket hasnt long been done and have fitted new reeds which i thort would cure it but still it happens ?!?.if any one has any ideas id be very grateful

cheers =)

I'd check:

Cable routing. Make sure it's not crimped somewhere and that the cable is not being pulled out of the ferrule where it meets the carb top,

especially when the bars are turned full lock.

Throttle housing: Pull the throttle apart and check for broken pieces or binding in it's operation.

Carb slide: Take the carb off and carefully inspect the slide for any scratches. Look inside the bore where the slide runs to be sure there

is no dirt or scratches. You'll need to look very carefully as it does not take much to stick a slide. I've had a carb on a new 2010 come

through from the Dellorto factory with some scratches in the upper bore of the body that caused it to stick wide open. It's a rare occurance

but is a possibility.

I doubt it's an air leak, those are usually consistant in symptoms and do not occur on a random basis.

Jon

[bowergas]

Dirt on carb slide would be my guess.

JB

[hgas]

ive had another look tonight doesnt seem to be anything wrong with the carb slide or an air leak of any form everything looks pretty normal realy,i had the same problem on my 08 250 but that was far more frequent and after i changed the reeds it was pefect .il just have to keep looking i think thanks for the replies though very much appreciated

[gas_gas_96]

sounds stupid but you could have something small in your engine possibly enterted through the exhaust that could be causing the pistons to jam open or something along those lines if non of the problems above fix it however i think they will but if they dont try a engine rebuild if you dont know what your doing buy a manual or bring up a exploded view on the internet

[spark]

sounds stupid but you could have something small in your engine possibly enterted through the exhaust that could be causing the pistons to jam open or something along those lines

You are right that does sound stupid, but thanks for the laugh!

On a serious note I agree with JSE. The fact that it is random would suggest the throttle slide getting stuck or cable jamming, or getting hooked somewhere. Also the symptoms of an air leak will be different to a slide being stuck wide open. With the slide stuck wide open the bike will rev up and have FULL POWER because there is the correct mixture (and a lot of it too) of air and fuel. You would need a massive air leak to let enough air in for the bike to have full power when the slide is down, and even then there would not be enough fuel to go with that massive air leak as the needle is all the way in the main jet hole. To demonstrate what I am saying, turn your tap off and let the bike idle. When the bike starts running lean as the bowl is low on fuel the revs will start to climb pretty high, but the bike will have no power and if put under load it will die.

[nath15804]

Hi, iv got the exact same problem with a dellorto carb, its on my old jtr 370. have not got a cluw why it does it, i also had the same problem with an old scorpa easy (fitted with a dellorto) i just ended up changing the carb and it solved the problem.

[joekarter]

Also check to make sure the vent lines out of the carb aren't pinched or blocked. This can cause the bike to go lean (like shutting off the petcock) and it'll feel just like a stuck throttle.

And yes, I know this from experiance...................resulted in the highest/shortest jump over a berm ever done on an 02 KX250

[steveo]

Had a similar problem.

The inner throttle cable where it is attached to the round lug the fits into the throttle tube had a single broken strand.

Easy to check.