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  1. #1

    No More Gas Valves....

    I had my second gas valve failure Thursday. Half the guillotine broke of into the cylinder. Luckily in only damaged the piston. Cylinder is fine. The whole guillotine broke off last summer and got a cylinder!!!!

    The stock ones are going back in and they will be pinned so this hopefully can never happen again. I am extremely tired of the Yamaha's repeated failures. It is just a matter of time until something else is broken. I have 0 confidence in this boat.

    Lowell's engine has so much power I don't think I will miss a thing by pinning them....


  2. #2
    Moderator OsideBill's Avatar
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    Can you post a picture of the valve? Also if you don't mind what springs were you running and how many turns in on the adjuster?

  3. #3
    Hydrotoys's Avatar
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    I'd like to see it too. I've never seen a gas valve destroy itself, and you've had two!

  4. #4
    GPRPITMAN's Avatar
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    Quote Originally Posted by OutlawGPR View Post
    I had my second gas valve failure Thursday. Half the guillotine broke of into the cylinder. Luckily in only damaged the piston. Cylinder is fine. The whole guillotine broke off last summer and got a cylinder!!!!

    The stock ones are going back in and they will be pinned so this hopefully can never happen again. I am extremely tired of the Yamaha's repeated failures. It is just a matter of time until something else is broken. I have 0 confidence in this boat.

    Lowell's engine has so much power I don't think I will miss a thing by pinning them....

    With lowells set up you will be fine on pinned valves.

  5. #5

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    same thing happened to me , i hate yamaha's man always break .

  6. #6
    Pistonwash's Avatar
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    Quote Originally Posted by Hydrotoys View Post
    I'd like to see it too. I've never seen a gas valve destroy itself, and you've had two!
    +1 Never, I have only heard of a couple and they were install problems.

  7. #7
    Happily Self-Employed WFO's Avatar
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    Fercho had one that tapped the piston once... and so did Jay if I recall correctly.

  8. #8

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    I feel your pain Outlaw. I happened to me about a month ago. Fortunately the shoulder on the valve prevented it from falling and so had no problems other than the valve.

    Mine was a clean break, right where the valve met the shaft.

  9. #9

    valve

    Both times the head of the valve dropped into the cylinder.

    Im not very good at pics, I might could send you one through an email and you post it.

    At WOT I started to lose rpms, about 40-50. I had been tuning the carbs on this boat and I was thinking it was started to lean seize at WOT so I killed the engine. When I killed it was still running with no seizure. I turned the high screws out to richen and when I hit the starter the engine was locked up. I swam and mile then pulled the head on found the remainder of the valve on top of the piston. The starter broke the top ring land on the #2 piston. Since the engine did not run the cylinder is fine. Just replacing the piston and rings.

    I was not using the outer caps or springs. The boat has so much bottom end Im burning a 16/26DF so I pulled the springs in hopes I could get some better holeshots without spinning.

    I plan to sell these cylinders and whats left of the valves during the winter and replaced them with Lowell ported non power valve cylinders. Im tired of this crap.....

  10. #10
    spud's Avatar
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    You understand why they broke don't you. By removing the springs and outer caps you allowed the valves to vibrate. The fatigue life is a lot lower on something when it vibrates. We use shaker tables at work to get quick results on repetative loads. Your gas valves being unsupported are doing the same thing.

    I guess if you use the stock valves you could unhook the servo motor and set them open. That would be better if you do not want the valves to acuate.

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