SBT Jetski Engines, Parts & Accessories

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  1. #1
    Sep 2005
    Raleigh, NC

    Red face Seadoo Rotary Valve damage - Advice needed

    Hi Folks,
    I'm helping a friend fix his 1990 Seadoo SP. I've found the problem that was causing a binding and clicking (popping) noise when the crankshaft was manually rotated clockwise.

    My question will be whether the damaged crankcase can be reused. Can they be resurfaced? I know the rotary valve clearances are very important, so I
    have my doubts. Definitely need a new rotary valve.
    Several photos of the damage can be viewed here -

    The obvious problem (now that I can see the rotary valve) is that the
    leading edge of the rotary valve shutter is damaged, and whatever foreign
    object it hit, got dragged around underneath the rotating disk and has badly
    scratched the mating surface of the crankcase. I'd estimate the the 4"
    diameter circular gouge is at least 1 mm deep and the right intake port has
    a 2mm notch taken out of the upper side. A chunk of metal the size of a
    metal thumb tack head which appears to be part of the foreign object that
    caused the damage fell out from behind the rotary cover when I removed it.
    It looks like the foreign object got scissored against the right intake port
    edge by the spinning rotary valve.

    Now that the rotary valve is removed, the engine turns freely and I can not
    feel any broken teeth when the rotary shaft turns. So I'm trying to work
    out where the foreign object came from. Next, I will be pulling the rotary
    shaft for inspection. The popping noise during rotation is no longer there,
    so the rotary shaft may be fine.

    Thank you for any advice on this.


  2. #2
    Feb 2004
    New Jersey

    Default Re: Seadoo Rotary Valve damage - Advice needed

    the case is shot , it can be fixed but it would be cheeper to go shopping on ebay for a case that is clean , or buy a SBT shortblock and have a warranty i would bet when you split the case you will find the rotory gear is damaged and shaft is bent
    PRIDE IN SERVICE<br /> <img src="" alt=" - " />

  3. #3
    Nov 2003
    Glendora, CA

    Default Re: Seadoo Rotary Valve damage - Advice needed

    Somebody just installed new pistons and they left something inside of the motor??
    Bill O'Neal <br>
    <a href=""

  4. #4
    Sep 2005
    Raleigh, NC

    Default Re: Seadoo Rotary Valve damage - Advice needed

    Yes, it seems so. I've got to give him some credit though. It was this gent's first time rebuilding an engine. No mentor, just a Clymer manual. I imagine lots of unfamiliar territory, a little scary, but at the same time the glimmer of excitement with thoughts of getting back out on the water.


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