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Rotary Valve - How to time

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  • Rotary Valve - How to time

    When installing a Sea-Doo 587, 657, 657X, 717, 787 or 787 RFI engine, your rotary valve must be timed. To do so requires a timing degree wheel, and the degree specification for your particular engine:

    90-93 SP, 91 GT, 91 XP, 93 SPi

    92 GTX, 92 XP

    88, 89, 94-96 SP, '94+ SPi, 90 GT, 93-'94 SPX, 93-'94 GTX, 93 XP, '92-'96 GTS

    95+ SPX, 94+ XP, 95+ GTX, '95+ HX, '96+ GTi, '97+ GTS, 1997+ GS, 1997 GSX, '97 SP

    Place a screwdriver, pen, etc., or use a TDC gauge in the front (MAG) cylinder through the spark plug hole. Turn the crankshaft to find Top Dead Center of this piston.


    Place a timing degree wheel over the rotary valve gear, aligning the 360 mark at the bottom of the front (MAG) intake port.

    Find the timing spec for your particular year and model. Using the inside track of numbers, make a mark on the case corresponding to the timing spec for your engine. This will be somewhere around 11 or 12 o'clock on the case. NOTE: do not automatically use the notch on the case to time by - you NEED to make sure it's timed correctly.

    Align the rotary valve as shown so that the port is open, and the edge of the valve matches as precisely as possible with the mark. NOTE: the valve is asymmetrical. Flip it around to find the closest match.
    Last edited by Ericka-SBT; 01-30-2008, 03:57 PM.

  • #2
    Re: Rotary Valve - How to time


    Over all these years, I have always been confused about timing.. You made this a lot easier than thought. Thanks for the great topic!
    Dan Solie -
    04 RXP (the "Instigator")
    94 xp (freestyle mods)
    95 xp (faster than the 94)
    JS550 (the toothpick & the loaner)

    For FREE Seadoo Manuals - Click HERE!!!!

    **** Please do not PM me. I don't do PM's.... Please post your question on the correct forum so that all can see and learn. Thanks! ****


    • #3
      Re: Rotary Valve - How to time

      Perfect. I just bought a rebuilt engine form SBT for a 1994 GTX. The instructions said to time the rotary valve opening to 147 degrees for that modal. WhenI did it it, didn't look right so I checked the shop manual, which said 130 degrees, the same as you. So you setteled it and the SBT provided instructions are wrong. Thanks
      Last edited by Technical Support; 06-07-2005, 06:33 PM.


      • #4
        Re: Rotary Valve - How to time

        I edited your post because there is no need to quote the whole dang article in your reply.

        Yes there is a type-o in the printed Engine Install Guide. We're sorry for the error.
        SBT Tech Support is here to help with your problems.
        We try to answer each question quickly and accurately.
        Please do not use Private Messaging for Tech Support, use the forums.