1991 LT250R, runs like a champ for a few hours, then idle goes from normal to sky high, its done it twice, both times i cleaned cables & pulled carb & air valve not stuck, i noticed both times was when it was almost out of gas, WHAT THE HECK? anyone?...

 

have you checked for vacuum leaks?

 

Ya, checked all connections, clamps, bands, ect...like i say, only does it when its almost out of fuel, WEIRD!!! im so lost on this one.

 

i've never heard of one doing that. i'm curious to learn from this one! hmmm

 

Ya, me too

 

Sounds like it's either running lean and engine revs up when you're running out of gas as you said (which can happen especially when hot) or you could have a crank seal problem? OPT

 

Sup OPT, i would think if its a crank seal it would do it as soon as the engine warmed up right?.. i really dont think its lean, its at 28:1 & my plug looks a bit rich if anything, why would it rev up when its low on fuel? Thats a new one to me OPT?

 

what do you mean especially when hot ? ambient temperature , are you think my quad is running hot ?

 

It can rev up when you are running out of fuel. Mine has done this before I just make sure tank is full. Might be good idea to spray carb cleaner all aound the carb, boot, reeds and cylinder base and see if it raises the rpm.

 

I got about half a tank in it now, im curious to see whats gona happen when im almost out and ill switch to reserve and then see, ill ride tomorrow then post, weather permiting...