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  1. #1
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Sherman's 1390 GPR

    Here is Sherman's ski from the Cayman Islands I'm building. It has (Group K) 1390 cylinders with power valves locked opened and ported by (Kevin at west coast porting). I put a new crank in it also new VF3 reeds from (WFO Rich) pressure tested the engine machined the head for proper squish and compression. Opened up the D plate for the big bore it has a set of 48 MM Novi's that i set up also i installed a (coco's) pump tunnel reinforcement. It has a jet works mod i modded his R&D plate to the FF mod also modded the trim tabs.

    I upgraded his old pump to a HO pump and a new Dynafly that i pitched, I install another pump shoe (Thanks Lee) that i set up and sealed. I installed (Leo's wedge) and i will set up all the handling. Once that is all done it will be ready for water test here is a video of it starting up with the rebuild engine.
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  2. #2
    WATER WOODY's Avatar
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    Sounds nice Jim. She's ready for some water.

  3. #3
    Thats nice build there............sounds good also, hum makes me wanna take a drive...........I think he's the one I sold a CF seat to...........few yrs back

  4. #4
    What an awesome winter project!!! Sounds great. How's the weather down there???

  5. #5
    XLR8's Avatar
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    Shermans 1390 gpr

    Glad you could help sherman out jim ,just curious how much port work was done to the cylinders? How much compression the engine have?

  6. #6
    Every adventure comes to an end........ Not Today! wreckingball's Avatar
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    I really like how the electrical box is mounted. How is it mounted and where is the battery located now? I think I see another change happening to mine if you could post a few more details about it Thanks

  7. #7
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by XLR8 View Post
    Glad you could help sherman out jim ,just curious how much port work was done to the cylinders? How much compression the engine have?
    I used another head because it was cut over 200 thousands, I was not able to get any compression before because the cylinders were off the motor when it came to me. But to get a 1390 to last i never run high compression i like to keep it on the safe side and that will give me a better top end then having to much compression that takes away from the top.

  8. #8

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    Looks good!

  9. #9
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    went out to test first run leo sitting on seat in neutral with carbs. set rich for break in 76.1 MPH. add 1 mph. for leaning back all the way and trimming add 2 mph. leaning the carbs. for proper mixture and once motor is broke in. I see it at the 78.7 to the 79.1 mph. range.

    Mind you this ski is going to the Caymans so it is not set up lose it's set up for handling and a 1200 grate.


  10. #10
    leo's Avatar
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    The ski ran great, good job jim.

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