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Thread: 150 psi head

  1. #1

    150 psi head

    I put a 150 psi pro tec head on my 2001 GP1200R and it improved the bottom end quite a bit, but it now seams like I lost a lot of top end. The ski hits top speed at around 3/4 throttle. So between 3/4 throttle and full throttle the ski does not really have a change in speed. Do I need to repitch the factory prop or get a different one. I don't see how this could be, I would think more throttle = more gas = more speed. Maybe I should use a GPS to make sure speed is not changing? I would think there would be a noticeable change in speed and rpm between 3/4 and full throttle though. Has anyone seen this effect and what can I do to gain back some of that top end without lossing that better holeshot? Since this site has a lot of experts on the GPR I thought I'd ask.


  2. #2
    james k's Avatar
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    You need a GPS,do you have a tach?? If not you might want to invest in one to see what rpms you are pulling incase you need to repitch your prop..If your rpms are too high i would say a 13/19 Dynafly would be a good choice but maybe some of the pros will chime in
    Last edited by james k; 10-25-2007 at 12:58 AM.

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    Moderator OsideBill's Avatar
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    James is correct you have to have a GPS and an aftermarket tach to tune properly, using dreamometer and factory tach is just guess work. Did you do anything else? D-plate. carb rejetting, F/A's? I recommend getting a tiny tach at minimum PET2100 if you can swing it is better.

  4. #4
    I also have a d-plate and free flow exhaust. What is the max RPM I should see?

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    james k's Avatar
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    I like to see between 7150-7170 in the summer heat and not over 7320rpms in the cold weather,60 degrees or so....this is just my preference and i have an efi ski....

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    Moderator OsideBill's Avatar
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    With properly jetted carbs I was in the 7200 range pulling a 14/20 DF Prop. There is a lot of variables to RPM's with a d-Plate FF and 150 PSI head you should not be running stock jetting if you are it is only time before you squeek a piston.

  7. #7

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    I am running now between 7150-7200 depending on the weather.

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    If you are running an old style type pump from that 01 model, a 13/19 Concorde would help you to see a better all around performance with out upgradeing the pump to use a dynafly inpeller.

    There are a lot of used concordes out there.

    You need to think about rejetting. There is a very good chance that you are now running lean.

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