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Power valve Open and Close

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Hello everyone I have a few quick questions. On a older model yz 125 like 1990 -1993 how far is the power valve suppose to open? Will this cause the bike to bog and half throttle? And will carbon build up in the exhaust pipe and silencer cause the bike to bog and smoke a lot ?? Please anyone with suggestions or answers please help me!

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Bogging and smoking a lot makes me think a wet side crank seal is leaking. A stuck power valve could cause bogging issues if it is carboned stuck. The ypvs power valve in these engines turn 90 degrees, and should move freely when disconnected from the linkage.

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The only thing I noticed is the power valve wasn't closing.. But how do I check the crank seal and that sounds like a lot of work..

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I have the same issue except I can see 1 of the power valves are stuck up thru the exhaust port. I havnt done much research on it yet. But my bike has no bottom end power it feels like I'm taking off from 3or4 gear. Once it hits mid throttle to full it runs like a champ with nothing but power. If anyone has any info if that would cause bike to have no bottom end power that would be great. It's a 00 yz125 with a 01 yz125 motor.

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I cleaned the power valve, as I'm riding I can defiantly tell when the powerband hits! But only problem is now it bogs when first take off and mid ways throttle before the powerband hit, what could this be

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