Rotax Power Valve question

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    Scott Mowrey

    Hello all,

    I was curious to know: After running a day or so with my kart, I disassemble my power valve for cleaning. Almost always, I found that the metal valve has unscrewed itself from the “diaphragm” (the round doo-hickey with the spring running around it) under the black cover. There is a hex-shaped nub on the top, but there is nothing on the red plastic screw that that hex fits into. It appears that the diaphragm rotates under vibration and drops the metal valve out during operation, effectively disabling the operation of the valve.

    How do I keep this from happening? By the way, I was told to back out the red adjustment knob 20 clicks from the bottom and to leave it alone. Sound advice? Thanks for any info!

    Doug Welch


    What your describe is extremely unusual. In fact, I’ve never seen it happen. Try this, take the power valve out. Remove the blade. Use a bit of red Lock-Tite and re-assemble. Use a 10mm wrench to hold it to seat the stud and blade. It should not come out. It is possible the threads in the diaphragm are stripped and not keeping the stud seated.

    16 to 20 turns out is best for the adjustment.



    Doesn’t the PV adjustment depend on which track you are on?

    I run:

    10-12 at the Track

    15 at IMI

    ?? at GJ

    Scott Mowrey

    Doug, thanks for the info, will try that tonight.

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