[ghost]

After a few trails riding for agout 40 minutes or so the bike started to rev super high then I woudl lose throttle control for a bit then it woudl go back to normal. A few minutes later it happen again. When it reved super high I pulled the kill swith nothing happened, then I turned the gas off it died. I let it sit for a few started it again and went for a few then it happened again. I was riding in the middle of the trail and didn't want to push it for miles so I tried my best to keep it going I thought I turned the gas off but I mistankingly place it on reserve, after that it ran fine.. Weird hugh? I checked the fuel level it wasn't that low maybe a little less than a quarter tank. Would fuel starvation cause this uncontrolled reving?? Or is it a ingnition problem. This morning I cleaned everything up, carb airfilter. Checked the throttle cable etc. All seems normal and in goog shape. I toped it off with fuel and took her around the yard. I let it get hot and it didn't do anything crazy. What could cause this? Any thoughts guys??

 

[blasterman88]

it sounds to me like a lean condition. could have been something clogging the main jet etc.....It could have been the bwol running dry, but definetly sounds like like it was lean. They call it a lean hang.....sounds like you got it under control with a good carb cleaning..

 

[2R's]

make sure the throttle cable (especially at top of carb & cap gasket ) is in good condition & is routed properly

 

[BLACKeR]

it sounds like a lean condition for sure. the fact that it stopped and wasnt consistent pretty much rules out air leak. being as the problem was fixed when you put it on reserve, makes it sound like you were starting to run out of gas, and this created a slightly lean engine.

in the future if its reving and wont turn off with the kill switch just smash your rear break while in gear with the clutch out.

 

[ghost]

Thanks for the replys, so a lean condition could cause this? It was really dusty up there and I rode behind my wife for some of the time. Maybe the carb got a little dirty. When I cleaned it was pretty clean though didn't notice any dirt or debris.

 

[mstohner]

it sounds like a lean condition for sure. the fact that it stopped and wasnt consistent pretty much rules out air leak. being as the problem was fixed when you put it on reserve, makes it sound like you were starting to run out of gas, and this created a slightly lean engine.

in the future if its reving and wont turn off with the kill switch just smash your rear break while in gear with the clutch out.

You could always pull the choke and that will cut it out also.

 

[NormalZ]

Plugged up gas cap vent or vent tube is also a possibility - check out the vent and vent tube...

 

[BLACKeR]

You could always pull the choke and that will cut it out also.

ive never heard that before. how would that work, especially if you have a lean condition making it rev?

 

[mstohner]

ive never heard that before. how would that work, especially if you have a lean condition making it rev?

not sure how it works but i have seen it done and my motorcycle votech teacher told me a to do that and he been teaching for many many years and racing both dirtbike and street bikes for 40+ years.

think about this what happens to a warm running engine when you pull the choke... it dies out.

 

[blasterman88]

You could always pull the choke and that will cut it out also.

depends, if its lean, then it would make the bike run richer.... it could be a variance of things....we had my 350 pro cross cylinder on the dyno this week, it was kinda lean first pass, raised the needle one clip and went up one jet size, the condition got worse. raised the needle again, and a bigger main, and GOT WORSE.....what was actually happening is i was running the bowl dry. the more fuel i gave it, the faster the bowl ran dry, and the leaner the air fuel meter would read. The fuel floats were too low, and thats what caused the condition....

 

[86 Quad R]

basing off your other post. at this point i would check out my fuel delivery. making sure that there isnt any blockage from the tank to the carb.

in your other post you mentioned that there was something going on at the rubber boot at the cap. may be a long shot here but, is there a possiblilty that dirt/dust could have made it's way into the cap? was there any trace of it when you cleaned the carb? is the slide show any signs of pitting(usually an indication of grit).

 

[ghost]

I will pull the carb again tonight and snap a few pics, I have a cable on order also.. Good ideas guys thanks..

 

[C-Leigh Racing]

Some 250R engines can be bad about sucking around the cylinder base gaskets. Wont do it when its cold but once it gets warm or hot, it goes to leaking & sucking air in around that area.

Wouldnt hurt to pull the carb back off & reset the float level a little higher so it maybe can maintain a little more fuel in the bowl.
Neil

 

[RebelBanshee]

since you say it ran fine after you put it on reserve, i would be very inclined to think it was just running out of gas(this will absolutely make it rev up). id fill the tank up and run it before i took anything apart.

 

[BLACKeR]

that is my opinion as well.

 

[07Tacoma]

my banshee has a problem getting gas when the tank is below 1/4. I just always ride on reserve and it fixes the problem. I know I run the risk of running out of gas but I don't want to be going up a hill and my bike has trouble with the fuel delivery. Just like the other guys stated I think it was a problem with not having enough gas in your tank to always be feeding your carb. It was low like you said and was splashing around making it hard for gas to get to your carb

 

[predator68j]

Some 250R engines can be bad about sucking around the cylinder base gaskets. Wont do it when its cold but once it gets warm or hot, it goes to leaking & sucking air in around that area.

Wouldnt hurt to pull the carb back off & reset the float level a little higher so it maybe can maintain a little more fuel in the bowl.
Neil

Mine had what sounds like the same reving problem, and it was the base gasket. It would only happen when the motor got hot enough. I also had a spacer that added to the issue. Sounded very similar to your problem.

 

[ghost]

If the base gasket is going are there any typical signs of wear, like leaking oil and stuff. The engine is pretty fresh less than 6 months old. Not like that makes a difference but just wondering..

 

[RebelBanshee]

there could be some oil leaking around the gasket. with the engine idling, spray some starting fluid on the cylinder base. The revs with jump if its leaking.

 

[dvickroy]

All bikes rev high when they run out of gas- I bet that's all that happened.


Fill it up and I bet it doesn't do it again.