951 porting advice - Page 2
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  1. #11
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 951 porting advice

    I have a 10 vane early 4tec pump here that I pulled off a GSXL. They are hard to come by. They are the same bolt pattern and use the same 951 size wear ring. A 951 impeller will also thread right on. The difference comes in when mounting one up. I can't remember if it was 1/2 or 3/4" difference needed in the driveshaft. The one I pulled it from just had all the mounts slotted to get it mated up. I don't see why a bit of mount slotting and a bit of trimming off each end of the driveshaft won't work.

    Pic of the early 10 vane 4tec pump.
    Attached Images Attached Images
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  2. #12
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    Re: 951 porting advice

    Is this something you are trying to sell?

  3. #13
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 951 porting advice

    Not really but I would. It needs a rebuild kit and wear ring.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  4. #14
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    Re: 951 porting advice

    I think the drive shaft needs to be longer? Is that correct?

  5. #15
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 951 porting advice

    I think so.....been a while. The GSX I pulled it from had slotting on the mounts and motor was shoved backwards.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  6. #16
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 951 porting advice

    Quote Originally Posted by Jet Cowboy View Post
    Generally called free porting.

    Quote Originally Posted by JC-SuperJet View Post

    Also known as SPI, Sub Piston Induction. The idea is to get a Fresh Shot of Oxygen-Rich Air into the Crankcase for a performance gain. But SPI is not recommended for 2 Strokes with Tuned Exhaust Pipes, because instead of Fresh Air, undesirable Exhaust Gases will make their way into the Crankcase. Remember that Tuned Pipes' Exhaust EXIT the Exhaust manifold and then some of it RETURNS to the Cylinder.

    Others may disagree with the above statement but there is no arguing that burnt, spent or Inert Exhaust Gases will contaminate the Crankcase Fuel Mixture.

    SPI mostly applies or works better with Engines with no Exhaust Mufflers/Chambers like some RC Model Airplane Engines(?).
    YUP, I disagree.

    My old super cylinder was free ported, but it is dangerous.
    OK to discuss theory. But if you are not familiar with it, just a
    little too much free porting, and our diaphragm carbs will not
    start the engine and the cylinder will be ruined.

    It may have been a tuning secret during the 80's and early
    90's, but since then other mods work better.

    I also disagree with the idea that widening the exhaust port
    is like free or easy HP.


    Bill M.
    Last edited by wmazz; 10-01-2021 at 04:23 AM.
    Horsepower == Speed, RPM != Speed



  7. #17
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 951 porting advice

    Free Porting works because cylinders tend to allow fresh fuel-air
    mixture to escape out through the exhaust port before it closes.
    There is more than one way for this to happen. Generally it is
    called short circuiting.

    When you supply fresh air or inert gas to the exhaust skirt of the
    piston, the transfer ports are open (to the crank case @tdc), the
    fresh air or inert gas is the first thing that comes out of the transfer
    ports when they open.

    When the short circuiting occurs, the fresh air or inert gas is the
    first portion of the new in-coming charge to go out the exhaust
    port, leaving a larger percentage of the original fuel air mixture to
    be converted into power.

    Over the years I have seen several different combinations work,
    and fail. There has not been a common solution for piped engines.


    Bill M.
    Last edited by wmazz; 10-01-2021 at 07:18 PM.
    Horsepower == Speed, RPM != Speed



  8. #18
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    Re: 951 porting advice

    Myself,

    Can you still buy that pump? Is there a part number?

  9. #19
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 951 porting advice

    I don't know of any new pumps available. You can still pick them up sometimes off Ebay--->https://www.ebay.com/itm/27543953283...temCondition=4

    I might even still have one around.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  10. #20
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: 951 porting advice

    I had one and sold it to Scottie Mac, he put it on a 96XP he was doing a Kawi engine swap in. There is a build thread here somewhere about his ski.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    WWSRD , What would Speed Racer do ?

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