1992 Yamaha Waverunner 650 LX - throttle seems limited
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  1. #1
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    1992 Yamaha Waverunner 650 LX - throttle seems limited

    New to this forum, appreciate any help I can get.
    Ski was running good last summer and for a few hours this summer.
    All the sudden it will only run half throttle when the throttle is pulled all the way.
    So I dumped in brand new rec90 premix gas, changed the fuel filter and plugs, unplugged thermo switch, but still no change.
    It doesn't spit and sputter, it run clean but just limited.
    I've called 6 dealers and nobody will work on it.
    Any thoughts on what I need to start investigating or working on?
    Appreciate the help.

  2. #2
    PWCToday.com Is My Home Away From Home fox river pwc's Avatar
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    Some video demonstrating it might help.

    Have a good look up inside the pump.


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    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    Fox is right I have seen some pretty chewed up aluminum impellers in these skis and they always make it cavitate and hit the rev limiter.

    At least yours is a 92 and has a Super BN carb instead of the round body carb they used on prior year skis.
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    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    Could the ski get up on a plane at wot?


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  5. #5
    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    I am only guessing, but I am betting you are on the rev limiter / limp mode.

    We see this quite often on the old Yamaha's, and I have seen it caused by most every item in the e-box, and even bad stators.

    Over heat sensor is #1, coil is #2, but could be CDI, and even a bad voltage regulator.

    A shop manual will give you values for testing, but is not always 100%. Sometimes you just need to swap out parts, one at a time.
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  6. #6
    Top Dog JC-SuperJet's Avatar
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    When was the Carb rebuilt last? The Regulator and Pump Diaphragms may be worn out. Carb has an Internal Filter. Rebuild with Genuine Mikuni Kit only.

    What is the Cranking Compression on each Cylinder?

    Have you trimmed the Spark Plug Wires back to good Wire at the Boot Terminals?

    The Items mentioned above are Basic Maintenance Items.

    Just because it's a Yamaha doesn't mean its going to run forever ; )

    Download a Free Service manual. It includes a Maintenance Schedule you should follow.

    Do some Basic Maintenance. Be Proactive. Don't wait till the Ski breaks.

  7. #7
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    Re: 1992 Yamaha Waverunner 650 LX - throttle seems limited

    Thanks a lot guys! I will start checking out these items. Impeller first!

    It doesn't plane out at WOT but by the pitch of the engine I can tell it is not reving wide open.
    Do you guys have a link to a service manual so I can get the testing values?
    Also, any pics of how the spark plug wires should look in the boots?

    Thanks!

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