Randomly my RPMs go through the roof!!! It is full of gas and the fuel valve is open but sometimes it just takes off for no reason, what gives? I took the gas tank off and noticed that the throttle cable is exposed to where you can see its "skeleton". Is it just a sticky throttle cable?

I'm starting to hate 2-strokes right now... plz help!

Edited September 16, 201114 yr by sweersz

So you're asking the internet if you have a sticky throttle cable, when the item in question is in front of you?

Any other thoughts of what it may be?

A sticking throttle does not operate on its own but can prevent the motor from slowing down after you shut off the throttle. Is that what happens? A cable routing issue can make the throttle open when you turn the handlebars. Under what conditions will it take off?

Basically after I shut off the throttle, the bike increases its RPMs by itself to where it gets extremely high. It's almost as if it's running out of fuel and the engine runs away but plenty of fuel is in there and my oil/gas ratio is fine too.

Sometimes when I'm in neutral and rev the bike, the throttle sticks but the RPMs do not increase after that which you mentioned. I just have to jerk the bike to get the RPMs back down.

Other times when I'm in neutral, the RPMs take off on their own without me having any influence. I would just be sitting there on the bike doing nothing and all of the sudden the RPMs skyrocket.

Could this be an air leak issue too? This problem never occurred in warmer weather (25 degrees C). This problem happened in colder weather (10 degrees C) so that means an air leak could be possible due to lack of thermal expansion on the rubber tubing by the carb? It seems pretty weather checked...

Thanks for the assistance. I don't want to die at 18.

Edited September 16, 201114 yr by sweersz

There could be a carb issue making it run out of fuel. Dirt floating around or maybe a sticky float valve could do that. I would clean the carb. While it is off, drain some gas out of the petcock to verify that it is flowing to the carb OK. Running some WD40 or oil through the throttle cable may loosen that up. A white spark plug would support a running out of fuel diagnosis. But, since it is intermittent, a dark plug does not disprove.

An air leak is possible but I have not heard of them causing intermittent problems. You could inspect the intake area for leaks and possibly try spraying on some soapy water to look for bubbles.

Does it ever bog when opening the throttle?

Edited September 16, 201114 yr by mcman56

Also check to make sure the vent hoses coming out of the carb aren't kinked or clogged.

I had the problem once on a small 50 cc 2 stroke.

The problem turned out to be the throttle spring above the slide wasnt tensioned enough and it would rise when it fancied causing the revs to rise sharply.

You may have a cracked rubber carb inlet manifold

An please replace that throttle cable!

Edited September 16, 201114 yr by NZRalphy