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  1. #11
    PWCToday Regular ROTZINGER's Avatar
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    Re: Pump physics, nerd talk!

    Yeah that's what most people say online... Most of the info is experience based and I still can't find an explanation that will be conducive to making estimations vs actually testing...
    Do you guys think a 6.5 could be reported to at least 6?


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    87 kawasaki X2 with all the westcoast bolt on goodies
    88 Kawasaki 650SX
    01 yamaha XL700

  2. #12
    PWCToday Regular ROTZINGER's Avatar
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    Re: Pump physics, nerd talk!

    Quote Originally Posted by Storbeck View Post
    Coincidentally, I've been digging around reading a lot of "what impeller should I use in my 650" threads lately, almost all of them say a skat 6.5 is too much especially with a Westcoast pipe. I have not tried it myself, but that seems to be what the vast majority of the threads on this forum say.
    Why do.you say that about the WC pipe? Is it that bad?

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    87 kawasaki X2 with all the westcoast bolt on goodies
    88 Kawasaki 650SX
    01 yamaha XL700

  3. #13
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    Re: Pump physics, nerd talk!

    Quote Originally Posted by ROTZINGER View Post
    Why do.you say that about the WC pipe? Is it that bad?

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    No idea I've never personally tried it, but again the consensus online is that the westcoast is more high rpm oriented.

    Kweasel is a better guy than me to ask that question.

  4. #14
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    Re: Pump physics, nerd talk!

    The WC pipe turned a little higher rpm than the Coffmans. You can bend impellers into whatever you want. The original 14/17 was just a bent 15.5. Everyone started cambering blades around 1990, they ran smoother. The rpm need to be up if you want power and speed. More pitch will slow down the engine and hurt performance, especially acceleration.
    Last edited by kweasel; 03-02-2021 at 12:57 AM.
    What exactly does the IJSBA do?

  5. #15
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Pump physics, nerd talk!

    ive ran a hooker 9/15 in my x2 with basically a stock 650 with a lengthened westcoast pipe, and a sbn44 carb and stock nozzles and it worked pretty well. accelerated well and would go 44 mph. im still running the same 9/15 with same nozzles behind a newmiller ported sp750, milled head for 95 octane, sbn 46, and blaster limited chamber b pipe setup and only now kinda feel like its slightly underpitched. im gonna bend the leading edge up 1 degree soon and see how it does. also will be putting a zeel on it as well.

    the newer design impellers are so much better than the old straight pitch impellers. the large hub design loads the engine better and the "swirl" cut also works much more efficiently which will allow more "dual" purpose so to speak with excellent acceleration off idle and still produce good top speed with no cavitation. impros.com sells the hooker impellers.
    96 superjet- rockered, -4, wide tray, adjustable footholds, kv148 mag setback pump, skat 7/14 impeller, rrp adjustable pole, blowsion ovp steering, 62t/62t, ada head, zeel A02T cdi, dual 44s, boysen power reeds, TNT SS chamber

    93-x2, newmiller ported SP750, milled head, R&D single 46 intake, sbn46, fpp blaster chamber pipe, hooker 9/15, umi, rhaas squirrel cage, dakine foot straps

  6. #16
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    Re: Pump physics, nerd talk!

    Quote Originally Posted by fastgtfairlane View Post
    ive ran a hooker 9/15 in my x2 with basically a stock 650 with a lengthened westcoast pipe, and a sbn44 carb and stock nozzles and it worked pretty well. accelerated well and would go 44 mph. im still running the same 9/15 with same nozzles behind a newmiller ported sp750, milled head for 95 octane, sbn 46, and blaster limited chamber b pipe setup and only now kinda feel like its slightly underpitched. im gonna bend the leading edge up 1 degree soon and see how it does. also will be putting a zeel on it as well.

    the newer design impellers are so much better than the old straight pitch impellers. the large hub design loads the engine better and the "swirl" cut also works much more efficiently which will allow more "dual" purpose so to speak with excellent acceleration off idle and still produce good top speed with no cavitation. impros.com sells the hooker impellers.
    I dunno, sure seems to me like those two motors have about the same port timing, the pipe on the 750 would come on lower if anything (maybe not, you said "lengthened" west coast, but still hard to imagine it's as long as a blaster limited) so your peak rpm would be about the same, the 750 should be able to pull a lot more impeller, or put another way the 650 would want a lot less impeller. Makes no sense to me that those two motors would be anywhere near optimal with the same impeller. I'm just looking at it on the internet though. Doesn't make me want to go get a 9/15 for my 650 if it's working well on a low port high compression 750.

  7. #17
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    Re: Pump physics, nerd talk!

    He said his 750 cylinder is ported, he didn't say how high.
    What exactly does the IJSBA do?

  8. #18
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    Re: Pump physics, nerd talk!

    Quote Originally Posted by kweasel View Post
    He said his 750 cylinder is ported, he didn't say how high.
    True. Seems like everybody on here is looking for the "bottom end hit" and goes with the low port cylinders and "don't raise the exhaust port", so I made the assumption but I shouldn't assume.

  9. #19
    PWCToday.com Is My Home Away From Home PrickofMisery's Avatar
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    Re: Pump physics, nerd talk!


  10. #20
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    Re: Pump physics, nerd talk!

    Yamahas get by with lower ports but Kawasaki pumps need to rev more. I would run 185 open with low compression and 190 with high on a 750. At least if I wanted to go reasonably fast.
    What exactly does the IJSBA do?

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