89 YZ 250 WIDE OPEN ON KICK.

[dc6587]

Hey Guys New to the site and have just bought an 89 yz250. I got it pretty cheap, But ran great the first week or so. Then started to bog out in 2nd and third at about 1/2 throttle. I took it home cleaned the carb, and now it kicks over but sounds like it is ready to blow up! The awkward thing is that it revs really high for about a sec then always shuts off without me doing anything. I have checked the cable, float, reeds, plugs, completely cleaned the carb.
Another thing is that on the right side of my crank case right near the tranny fill bolt and the power valve (i think) there is a small amount of oil that leaks slowly when i had rode hard. I have heard of the airleak possibility, but was looking for a couple more opinions. Anything will help, Greatly Appreciated!

Dan

[Willum]

I know if I forget to turn my gas on my bike will act like this once the bowl runs out of gas.2 strokes will scream when they run extra lean. I would check the crank seals on both sides for leaks a leaking seal will cause a lean condition making it scream then move on to the carb again and making sure everything is working and its getting fuel in the motor right. Good Luck!

[dc6587]

Gas is on, but good looking out, am in the process of strippin it down, and looking at the seals, do you know if the powervalve would have something to do with it? I keep hearing about it and I think the small leak I mentioned is coming form the push rod seal, not sure though. Thanks for the help.
Dan

[Conrad#356]

Originally Posted by dc6587

Gas is on, but good looking out, am in the process of strippin it down, and looking at the seals, do you know if the powervalve would have something to do with it? I keep hearing about it and I think the small leak I mentioned is coming form the push rod seal, not sure though. Thanks for the help.
Dan

You might check the fuel petcock. could be clogged and I don't know how they were built in 89 but on any YZ ive seen there is supposed to be no oil in the pushrod housing so that seal may be bad. don't know why it would cause it to start wide open though.

[dc6587]

Have'nt checked the petcock yet but just curious, you said there should not be any oil in there, near the pushrod seal? I am taking the rightside case and the power valve case off today just to have a look but I will keep ya posted, thanks for the help man
Dan

[Conrad#356]

In the powervalve cover on the front of the cylinder there will be some unburnt oil, thats normal. But where the pushrod linkage is on the right side of the cylinder there should be no oil in there.