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Thread: Speed on GP1200

  1. #1
    enforcer's Avatar
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    Speed on GP1200

    O.K. everyone here is the actual test result for my 2001 Yami. . I'm actually upset because I didn't get the speed that I originally thought it would get me so here it is.
    outside temp. 92
    lake temp. 82
    humidity high as hell ( feels like Louisiana)
    wind 5-15 mph

    here is the list of mods done so far.
    Stock head cut by someone reputable yielded 120 p.s.i. all across even
    Stock carbs re-jetted with accel. pumps and choke plate removed
    VF3 reeds without stuffers
    D-Plate with sensor chip
    Free flow
    05' pump with stock nozzle fitted with a stock box DF14/20
    Jim's FF plate with angle set at .980
    Stock sponsons steeped as per speed package
    Stock oil injection retained
    Stock trim tabs and no shimming yet

    on three bars of gas gps'd at 70.0 actual after 4 back to back runs and an average of more like 69.4.........
    guys I have gone throgh the pump shoe and even grinded the pump shoe to the R & D intake grate and it is matched and the pump is sealed pretty good and nothing is hanging down.
    I just want to say thank you to Billy ( RX951)
    Jeff ( JEFFSNTX)
    Jim (JIMS 1300
    and Fernando ( FERCHO)
    and everone else who has walked me through some pain in the ass work ! Further I would also like to add that in no way am I complaining but I was expecting a little more.
    Also wanted to let everone know that I raced a Sea-Poo RXP with rear intake and I suspect the Phirana wheel but they wont say and we were dead even top end wise but took me out of the hole by approx. 3 boat lenghts Oh well I guess I need to see about more adjustments and to see if any more speed is available....guys any suggestions?


  2. #2
    My son (mohawk man) jeffsntx's Avatar
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    What kind of RPM's?

  3. #3
    enforcer's Avatar
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    Oh sorry 6990 was the highest I saw

  4. #4
    dhoad's Avatar
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    I'm guessing the experts will chime in with some ideas on things, but in that heat and humidity it is not unusual to be down on top speed by 1 or 2 mph and 100+ rpm

  5. #5
    Chrisrokc's Avatar
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    That all sounds about right speed wise to me.

  6. #6
    Brian Thomas's Avatar
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    Hmmmm, My thought is the speed is off atleast 2-3mph?

    I have `01 setup very similar:
    stock head 140psi
    stock reeds
    D plate
    Stock carbs w/ chokes and accel pumps removed
    05 pump w/ 14/20 DF thru 85mm nozzle
    800 grate
    Jim's FF plate set @ .950

    Temps very similar. Elevation 1000ft.

    Typical is 72-73mph @ 7000rpm

    -BT

  7. #7
    Chrisrokc's Avatar
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    Where are you riding though? Lakes? Rivers?

    Also he doesn't have his head cut... well to a high compression. That is a lot of prop for an almost stock head to turn on a 1200. Hell my 1300 had an issue.

    Also are you two running tabs or no tabs?

  8. #8
    Duke's Avatar
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    Compression sounds a little low to push that prop. Might want to check your PVs to and see if they are opening all the way. RPMs are to low IMO. Where is the pump shoe set at?

  9. #9

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    I agree with Duke the compression is low if you have a good quality gauge and good battery/starter for spinning the motor to test compression and have the throttle full open. 120 psi thats a few pounds lower than a stock head ususaly has. Get a good snap-on or Mac gauge and re check your numbers. You usualy need 140-150 psi on 93 octain gas to get the best out of your set up you can.

  10. #10
    enforcer's Avatar
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    O.K. the stock head that was cut was supposed to yield around the 135 p.s.i. mark and I was told to remove the middle gasket and run the upper and lower gasket.I sealed them with the copper coat spray by permatex and it seems to have sealed well based on the compression test.I was told that the stock head would hold 135 p.s.i. based on the cut of the head and 2 layer gasket.Duke thanks on the PV's I checked and all open easliy and engages well and I checked and all open fine. The lake that I ride on is usually 6-12 inch chop but where I was was almost glass with slight ripple.The stock head was cut right at the deck height is on the bevel portion. Should I use a different head or just buy a new stock head and have it cut? I prefer not to buy an aftermarket yet unless someone has a good one because I have future plans to go 1390 Big Bore

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