SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
    Sep 2004
    From
    Mississippi
    Posts
    6

    Default Seadoo Rotary bearings. 720 motor.

    Summary:

    -Engine would only turn so far one way or another.

    -Upon tear down, I found a bent rotary valve. The cylinder that failed blew out the Lower rod end bearings and bent the valve.

    -The rotary valve shaft brass gear got a bit boogered up from the bent valve and the engine turning.

    -The rotary bearings must have gotten some brass bits in them. They are a bit rough after removing them from the case and cleaning them. That could be the only way they could be bad since the rotary shaft chamber was full of oil, and neither of the seals on the main crank had failed on the interior to allow debris into the oil bath area. There were also bits of brass in the oil bath chamber from the rotary shaft gear.

    Question:
    So, is it safe to try and clean these existing bearings of brass? What is the part number for new bearings? Where might I find new ones? I have every part for a rebuild including a new brass gear. (Crank, seal kit, pistons, gaskets.) The only thing I don't have is these bearings.

  2. #2
    Joined
    Nov 2003
    From
    Glendora, CA
    Posts
    6,846

    Default Re: Seadoo Rotary bearings. 720 motor.

    No, take those bearings to any bearing supply store and buy new bearings. You are talking about $10.00 worth of savings by trying to clean them. It isn't worth it.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

  3. #3
    Joined
    Sep 2004
    From
    Mississippi
    Posts
    6

    Default Re: Seadoo Rotary bearings. 720 motor.

    Thanks Bill. I read most of your posts. I wasn't sure the local bearing supply places would have them. Searches on the 'net turned up very few specific results for these particular bearings.

    When do you actually find time to work on PWC's since you are on here a lot!??

    This will be my third project, overhaul 'Doo.
    Thanks again.

  4. #4
    Joined
    Aug 2001
    From
    Las Vegas, Nevada
    Posts
    1,220

    Default Re: Seadoo Rotary bearings. 720 motor.

    This is a re-post from an earlier post, I put it here for your information:


    With a "boogered up" brass gear, and bearings needing replacement, plus the damaged rotary valve, I would suggest the following parts from right here at SBT:

    Rotary Valve Shaft Assembly: http://www.sbtontheweb.com/Merchant2...tegory_Code=43

    Rotary Valve:
    http://www.sbtontheweb.com/Merchant2...gory_Code=40-1

    Gasket Set:
    http://www.sbtontheweb.com/Merchant2...gory_Code=40-1

    Although the "complete gasket set" is what I recommend, as it leaves no room for error, you can pick and choose the items that you need from the list that is provided on the page.
    John Kubiak
    Powersports Technical Training Professional
    Las Vegas, Nevada
    Sea-Doo Tech 13736
    PWC Tech since 1988 (22 years)
    PowerSports since 1976 (34 years)
    NEVER BUY TIRES AT A "BLOW-OUT" SALE
    Please do not use Private Messaging, use the forums.

  5. #5
    Joined
    Nov 2003
    From
    Glendora, CA
    Posts
    6,846

    Default Re: Seadoo Rotary bearings. 720 motor.

    Bearing number SKF 6203TN9/C3 or equievlent.


    But beware. If you reuse the RV shaft it will fail again as they always get bent when the brass gear shears off the teeth.
    You would be best to buy the complete RV shaft assembly and the one case bearing that does not come on the assembled shaft. SBT has all the parts you need.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

  6. #6
    Joined
    Sep 2004
    From
    Mississippi
    Posts
    6

    Default Re: Seadoo Rotary bearings. 720 motor.

    Once again good advice. I had gotten the shaft all apart tonight and Mic'ed it with a runout guage. Not only is it bent, it's slightly twisted along the splines from the valve hitting the side of the intake hole. I guess I figured the brass gear would suck up the damage. WRONG. The shaft must be made from a milder unhardened steel. The brass is surprisingly intact. It only has some dings inside the teeth.

    I had already gone down and picked up a couple of bearings.

    Oh well, What's another $80 plus???

    The smaller case bearing number is 6201-Z. That was the one I took out. The replacement was a standard 6201 with a seal on both sides. I pulled off one side bearing seal so the oil bath can get to the balls inside.
    Last edited by schmeddz; 09-26-2005 at 08:46 PM. Reason: Added bearing information about small bearing.

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