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Old 20-10-2018
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Nutty Nutty is offline
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YZ250 tuning tip

Re: power valve actuation on WR/YZ 250s. The problem is that the RHS segment vent was deleted by the pipe builders. I sussed this out building 250Superkart motors. The RHS valve develops an oil-film seal which delays the PV opening, a pneumatic governor of sorts.

Buy a hose and a 90 degree fitting and make the RHS PV cover vented, the same as the LHS one. You'll have to clearance the pipe with a ball-pein hammer. The fitting press-fits with some bearing mount or wick-in.

Best (and cheapest) mod ever to get the 250 going.
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Old 20-10-2018
BigE BigE is online now
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photo would be good?
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Old 24-10-2018
eXc eXc is offline
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interesting idea. Have you done this on many, and how long did you run them for?
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Old 2 Weeks Ago
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Quote:
Originally Posted by eXc View Post
interesting idea. Have you done this on many, and how long did you run them for?
Dozens and forever is the short answer. Strangely, long motors sold for Superkart kits have them standard.
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