02 CR250 engine trouble

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10/11/2018 2:47 PM

Wanted to ride on Sunday so started the bike up today. Was extremely difficult to start but when it finally fired it revved like crazy. Had to shut the fuel off to get it to die. What do I need to do? It ran fine a few weeks ago. Thanks for the help gents.

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2007 YZ250
2007 YZ450F

Specialized Bikes

10/11/2018 3:07 PM

You got an air leak somewhere

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10/11/2018 3:08 PM

What’s the easiest way to figure out where it coming from?

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2007 YZ250
2007 YZ450F

Specialized Bikes

10/11/2018 3:49 PM

Spray carb cleaner around your air boots on your carb, cylinder gasket, and head gasket. RPMs will drop when you find it. If its not any of those, youll need crank seals.

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10/11/2018 6:23 PM

If it were me I would suggest removing the pilot jet and cleaning it. If the bike set for more than a week, most likely the pilot jet has partially clogged with dried fuel and plugged at least some of the small holes in that jet and creating a very lean condition which can cause it to rev to the moon.

Paw Paw

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10/11/2018 7:59 PM

I had the right crank seal back out on mine. It caused intermittent lean running rev and then it would suck oil and blubber. All depended on the bike leaning.

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The older I get, the faster I was.

10/11/2018 9:39 PM

Paw Paw 271 wrote:

If it were me I would suggest removing the pilot jet and cleaning it. If the bike set for more than a week, most likely the pilot jet has partially clogged with dried fuel and plugged at least some of the small holes in that jet and creating a very lean condition which can cause it to rev to the moon.

Paw Paw

This. I doubt you suddenly developed an air leak in that amount of time.

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10/11/2018 10:55 PM
Edited Date/Time: 10/12/2018 12:48 PM

Paw Paw 271 wrote:

If it were me I would suggest removing the pilot jet and cleaning it. If the bike set for more than a week, most likely the pilot jet has partially clogged with dried fuel and plugged at least some of the small holes in that jet and creating a very lean condition which can cause it to rev to the moon.

Paw Paw

omalley wrote:

This. I doubt you suddenly developed an air leak in that amount of time.

Agree. Another thing to consider would be if the weather has cooled down in your area the last few weeks. It's possible you need to adjust the air screw to add more fuel. Try turning in the A/S a 1/8 of a turn at a time to see if it helps before pulling the carb apart to check for a plugged PJ. Make sure the engine is at operating temps before making any adjustments.
If you end up with less than a turn out on fully closed you will need to go up 1 size on the PJ & start the process over till you get a normal idle.

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Speak softly and carry a big stick.

10/12/2018 12:01 AM

My 07 cr250 did the same thing it was the left side crank seal behind the flywheel.

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