Benifits of Stroker Crank? - Page 2
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  1. #11
    I dream skis FreestyleRiverRat's Avatar
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    That is exactly what I was thinking. I want to produce a motor that is powerful, durable and smooth. Since the cases are set up to already accept the stoker crank they should provide some nice flow through the ported cylinders. My 650 motor is doing well for me currently so I will ride that for a while, then when it is time to freshen it up send the crank out to be rebuilt, have it trued and welded and put it in the 61x cases. I am planning on having JR magoos do the porting this winter. Sould be a nice build up. My 650 currently is ported by Group K for mid to top end with a protec pipe, head, lightened flywheel, DG performance 38's and MSD enhancer. Nice smooth and fast as is, but the 701 should give me the low end I'm looking for.

  2. #12
    Resident Guru freestylegeek's Avatar
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    Quote Originally Posted by FreestyleRiverRat
    ...I'm having JR magoos do the porting this winter...
    If your talking to Paul, you'll have a great motor next spring!
    Sounds like you're definitly doing the right thing. 8)

  3. #13
    HATZY
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    Re: Benifits of Stroker Crank?

    Quote Originally Posted by mile9c1
    Quote Originally Posted by SuperJETT
    Here's a good article from a different perspective that specifically talks about 650/701's.
    http://www.hpt-sport.com/stroknot.htm
    I must have missed something... his program estimated 50 horsepower for a stock 701? Which formulas are he talking about?? Why does he start off by saying the Kawasaki 650 engine makes better power than the 701??

    I think he knows a lot about engines but he needs to rewrite that article; the Group-K articles are much easier to follow. It sounds like he likes strokers, but he didn't address the piston-speed issues that GroupK does, nor real life test results. Even his program generated horsepower numbers are vague.

  4. #14
    HATZY
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    Re: Benifits of Stroker Crank?

    What George meant was that Kawasaki, with its longer stroke(78mm) to bore ratio, makes more power than Yamaha's short (68mm) bore to stroke ratio. Yamaha has addressed this issue, after the work done by Dan Lamey, and incorporated a 78mm stoke in the newer(66v) power valve motor. It's all in the combination of stoke length, rod length, and bore size. Kawasaki's formular for the 650 is better than Yamaha's 701.

  5. #15
    PWCToday.com Is My Home Away From Home mile9c1's Avatar
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    Re: Benifits of Stroker Crank?

    The Kawasaki 750 is a only 74mm stroke.

    It's also about the porting, and the GP800 porting puts all other engines to shame.

  6. #16
    PWCToday Regular freestylejetski117's Avatar
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    Re: Benifits of Stroker Crank?

    crankworks will build a 5mm longrod

  7. #17
    PWCToday Regular freestylejetski117's Avatar
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    Re: Benifits of Stroker Crank?

    mile 91 what bore are you running on your able motor

  8. #18
    PWCToday.com Is My Home Away From Home mile9c1's Avatar
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    Re: Benifits of Stroker Crank?

    Quote Originally Posted by freestylejetski117
    mile 91 what bore are you running on your able motor
    I sold it last year, but it was a stock bore (81mm) and it had a 5mm stroker crank with stock length rods.

    Next week my X-jet will be getting a 6mm stroker engine

  9. #19
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    Re: Benifits of Stroker Crank?

    good for freestyle

  10. #20
    PWCToday.com Is My Home Away From Home Benflynn's Avatar
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    Re: Benifits of Stroker Crank?

    Quote Originally Posted by HATZY View Post
    What George meant was that Kawasaki, with its longer stroke(78mm) to bore ratio, makes more power than Yamaha's short (68mm) bore to stroke ratio. Yamaha has addressed this issue, after the work done by Dan Lamey, and incorporated a 78mm stoke in the newer(66v) power valve motor. It's all in the combination of stoke length, rod length, and bore size. Kawasaki's formular for the 650 is better than Yamaha's p701.
    how can Kwai formula be better? 701 crushes the kawi, first time u ride a slightly modded 701 u sell ur 650, sell ur small pin and buy a sj

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