I have an 87 Suzuki LT250 QuadRacer. It's starts great, but then it will all-of-the-sudden just surge up, and up, and up. This is after sometimes less than 10 secods of idling! I never let it idle too long either, cuz i know that they can get carboned up and have probs, so I only let it get warm. But once it revved sooo high that I actually jumped off the bike and ran away from it cuz I thought she was gunna blow. It ended up getting like 12,000 for about 30 seconds, and then killing out. It's happened numerous times and i've even had it into the shop and he filed on an idle screw, he had it running great, and it ran great for about 2 weeks, now it's starting to happen again! What's goin on?? (Appreciate feedback)

 

sounds like an air leak. could be around your intake manifold(boot between carb & reed valve) or any of the seals or gaskets on the botom end or cylinder base gasket. while it's running spray short bursts of carb cleaner around these areas, usually you can see where the problem is (if this is the case) by carefully watching where the mist goes & listening to the engine while it does it.
also check to make sure your throttle isn't sticking, due to grit on the slide or cable being worn.

my brother had this prob on his '90 LT, we did a full engine rebuild with new crank & everything, got a factory carb(had an old hunk of crap 38 on it) & thumb throttle off ebay, rebuilt the carb, put on a new cable, and went to a rad valve.... not cheap but got the problem fixed.

 

dual-sporter's right, sounds like an air leak. And a major one at that. You don't want to run that engine anymore than you have to, because an air leak is a major lean condition, and can easily seize up your motor leading to more cost. One of the best way to check if the can of starter fluid don't work is to make a leak down tester. It's not that hard I made one for mine because I was fouling plugs at high RPM, go to www.duncanracing.com they have a good read up on pressure testing.

 

aite dual sporter; thanks alot for your input. the only thing is that the mechanic already did the air leak test and saw nothing... so i'm not sure what's going on. but thanks and i'll have to check it again. thanks.

 

mine's fouling plugs too! this is all kinda scarin me. thanks fellas, i'll have to look at it some more...

 

have your mec pressure test it again . it sure does sound like an air leak . it could be at the rear cylinder base gasket or even a seal .but like the others said dont run it any londer than nessesary .let us know ..

 

aite donzilla [img]i/expressions/face-icon-small-wink.gif[/img] thanks for your input. i'm gunna stop riding it just because when it surges like that it's so loud it makes me want to crap my pants. Not to look like a *****, but that thing really hits the high-note. my dad and i estimate it at running around 14,000 when it went nuts the one time.
--so basically you guys are saying that surging to high rpms and plug-fouling is a symptom of an air leak? I just want to make sure so my dad and I know what to look for.
thanks again fellas.

 

yup py puppy .i would have to say that thats your prob . if it was just the carb it just wouldnt run right , not surge like that . an air leak will let the engine rev and as it sucks more air the more it will rev . hope this helps [img]i/expressions/face-icon-small-smile.gif[/img][img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-disgusted.gif[/img][img]i/expressions/face-icon-small-mad.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-smile.gif[/img]