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Sticky Throttle and broken collar bone

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I was out riding a couple weeks ago on my rm250. Just finished breaking in a new piston that morning and was on my last lap of the day when my throttle stuck wide open on me. I had just shifted from 4th to 5th and i was on some sand whoops. let off the throttle and it stayed wide open in the powerband 5th gear. I pushed forward on the throttle but it was all the way closed. I bailed because I was 20 feet from going over a berm and into a barbed wire fence.  Broke my collar bone and doc said im out through january.  What caused the throttle to stick? i tore the carb apart and everything seemed normal? Any advice would be great

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The throttle did not stick, as you described it.....since you did manually push the slide closed with throttle tube

 

More than likely, what is happening, is the stator side crank seal is just starting to leak; when you get maximum vacuum pressure happening, the seal leaks in fresh air, leaning out the mixture and giving you 'run-away' throttle. Closing the slide won't help, as the air is getting in through the seal that leaks.

When this happens, even the kill button won't do anything......the motor runs wide open until you put in against a wall and let out the clutch, or, crash it

 

Sorry to hear about your injury

 

Replace both crank seals.

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Same issue. Its happened two times. One approaching a jump and the other going in to a corner. The jump was very scary! Both times I pulled the clutch in by instinct, and all was well ( although it took me a few minutes to regain confidence to hit the jump again!!).

After that I took apart the carb and cleaned it. It hasn't happened in several rides but after reading this it looks like I need to do the crank seals. No idea how to do that ... I hope my manual covers it.

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I was out riding a couple weeks ago on my rm250. Just finished breaking in a new piston that morning and was on my last lap of the day when my throttle stuck wide open on me. I had just shifted from 4th to 5th and i was on some sand whoops. let off the throttle and it stayed wide open in the powerband 5th gear. I pushed forward on the throttle but it was all the way closed. I bailed because I was 20 feet from going over a berm and into a barbed wire fence. Broke my collar bone and doc said im out through january. What caused the throttle to stick? i tore the carb apart and everything seemed normal? Any advice would be great

Ugh! Out until January? Damndamn! That sucks

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in all my years of messing with two strokes and having  a few runaways   i have never heard of one taking off while  uncontrollably under load like a PWC in the water of the bike in gear

 

just on the stand  

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