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  1. #1
    YudLuz2's Avatar
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    How many rpms did you gain when you ported your 1200 motor?

    I was just wondering for the experts out there how many rpms they actually gained on a 1200 cylinder when they ported them for triple
    pipes. Or how many rpms was the 800 cylinder porting give you over
    the 66V 1200 cylinder with triples. I wondering if I should port these cylinders myself and do a little more playing around with this setup before going big bore. My other concern is getting the prop pitched correctly and returned to me on time for a bigger motor. I went out yesterday and turned my stock 14/20 Dynafly 7850 rpms. That was on a heat soaked motor with temps around 87 degrees with no carb tunning, just putting it
    in the water and riding. Still have no reeds or any other mods added since
    my single pipe runs. Will be adding V-force 3 soon. Ben


  2. #2
    ABBOTT's Avatar
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    assuming that you are testing with the same prop and pump, and just adding the port job - i would say anywhere from 150-250 (or 2-3 mph)depending on who and how much is shaved off in the porting process. I am assuming that the heads are getting milled at the same time to about 160psi--i factored that into it as well.

  3. #3

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  4. #4

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    Quote Originally Posted by ABBOTT
    assuming that you are testing with the same prop and pump, and just adding the port job - i would say anywhere from 150-250 (or 2-3 mph)depending on who and how much is shaved off in the porting process. I am assuming that the heads are getting milled at the same time to about 160psi--i factored that into it as well.
    And then you get to repitch your prop and really see some gains!!!

  5. #5
    WATER WOODY's Avatar
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    I gained around 225rpm going 1300 and porting.

  6. #6
    philip_gpr's Avatar
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    I don't think I would bother just porting 1200 cylinders, better to install something bigger an then do porting

  7. #7

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    Quote Originally Posted by WATER WOODY
    I gained around 225rpm going 1300 and porting.
    You shouldn't gain much from just going from 1200 to 1300 should you??? I thought the big RPM gain were from the porting?!?!?!?

  8. #8
    ABBOTT's Avatar
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    Quote Originally Posted by RXPkiller
    Quote Originally Posted by WATER WOODY
    I gained around 225rpm going 1300 and porting.
    You shouldn't gain much from just going from 1200 to 1300 should you??? I thought the big RPM gain were from the porting?!?!?!?
    all depends on the torque curve and the prop pitch. If you take the stock prop off a plain 1200 and stick it on a 1300, then you might be +100. But if your comparing a stock 1200 and a stock 1300, then the rpms should look very similar - being that the 1300 stocker is bent just a tad bit higher to compensate for the 100cc gain in displacement.

    Different story for comparing stock 03's/04's to the 05's/06's because of the removal of the PV's and upgraded high pressure pump. I would venture to say that the stock rpms for all 6 years of the gpr production are very similar unless you take a prop from the 00-01-02 1200 years and put it on an 03-04 1300.

  9. #9
    philip_gpr's Avatar
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    when going from a stock 1200 you gain significant rpm with

    1200 to 1300

    porting

    raising compression

    VForce reeds

    aftermarket CDI

    everything adds a bit (my guess is the 1200 to 1300 provides the biggest single gain)

  10. #10

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    Interesting! That's cool...

    What about JUST porting a 1300, all else equal?

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