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  1. #1

    Post 2010 VX Stuck Exhaust Valve

    2010 VX Deluxe Waverunner
    Here's what she looks like when you have no compression on one cylinder. This is the two exhaust valves for one cylinder. One valve pad is up - one is down (and not contacting the cam lobe). Anyway, this engine looks awful clean from the valve top side. What ashamed it looks like a head pull off job for one sticking valve. Anyone ever tried to free one up from the top side before? Thanks!
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  2. #2
    Probably bent anyway right

  3. +1 by:

  4. #3
    Quote Originally Posted by jsmob View Post
    Probably bent anyway right
    What would cause a single exhaust valve to bend? On really old automotive engines it's possible to unstick them by soaking the guide with PB Blaster and giving the valve stem a whack. This is when it's frozen due to rust or excessive carbon.

  5. #4
    Aren't the exhaust valves interference-fit with the piston at TDC?

  6. #5

    Join Date
    Mar 2010
    Long Island, NY
    Unlike the Kawaski 4-stroke motors, the Yamaha MR-1 motors have only one spring on each valve. So even a little resistance on the valve can cause it to stick open. A bit of carbon or rust build-up on the stem can keep the valve from closing before the piston hits TDC. I'd bet the valve is bent and there are marks on the top of the piston.

  7. #6
    Roger that. Engine is all ready to come out in the AM. I have used a local head shop before that does great work and confirmed they have worked on these tiny Yamaha OHC engines. She's getting a valve job and inspection. I'll post a picture when the head comes off. Can't believe the amount of forum/web searching I did with no results. Must not be too many of them out there with valve problems.

  8. #7
    boudin's Avatar
    Join Date
    Oct 2009
    Lake Livingston, TX
    I have fixed several of these, the most recent two weeks ago. A trick that WFO taught me. This happens if the ski sits for a long period of time with water in the waterbox. Exhaust valve(s) can develop a little rust on the stems and stick.

    Pull the cam tensioner, cam covers, and cams out. Pull out the valve bucket/shim for the stuck valve. Attach a leak down tester to the cylinder and bring the pressure up. Spray penetrating oil around the valve area. Take a brass punch and start tapping on the valve until the leak down starts coming up to normal.

    Reassemble--see the shop manual if you need to.

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  9. #8
    Thank you Greg. I’ll try that next time. I removed the head and polished all the exhaust valve stems well this time. Quite a lot of carbon buildup on them. Intake valves looked new. Easy job, just a bit time consuming. Surprised the oil tank needs to come off to remove the head.
    Runs like new.

  10. #9
    Next time. Get a brass punch and bang on it a few times. Happens all the time here

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