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Thread: Real RPM

  1. #1
    bex's Avatar
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    Real RPM

    I have a question concerning the actual RPM my engine is doing. I have about 10 hours since a top end rebuild on a 00' GP1200R with 164 hours total time.

    Ski is operating fine after tweaking the PVs, #3 PV pin cut loose and nearly dropped down into the cylinder, so I went with the R&D PVs, excellent build quality. Anyway, I was running a 68N00 12/18 prop and was getting about 6.8 to 6.9K RPM on the stock rpm gauge @ 57mph on the GPS.

    I was curious that I wasnt getting enough out of the engine or the breakin process left me wanting, therefore I changed the prop to a solas 13/19 concord and R&D ride plate just to get a bit more speed out of the ski.

    Now, with the mods, freeflow exhaust, d-plate, concord 13/19 and R&D plate, my RPMs have dropped to about 6.5K 6.6K on the stocker gauge @ 63mph.

    Performance wise I have no complaints about holeshot or top end, just wanting to know why I am not getting 7.1k on the RPM? If I can turn more RPMS I know my top end would increase to about 65 which is what these skis should be good for out the box.

    I did reason to expect a drop in RPM with the steeper pitched prop.


  2. #2
    Moderator OsideBill's Avatar
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    What are your carb specs? what changes did you make there?

  3. #3
    bex's Avatar
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    Actually Bill, I didnt make any changes to the carbs at all. I have been debating whether or not to send em in to have them properly adjusted or to try and do them myself.

    They are stock jetted and I am running premix at 36:1 Amsoil Interceptor.

    Could lack of rejetting be holding me back?

  4. #4
    Happily Self-Employed WFO's Avatar
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    First off, the stock gauge is junk for tuning carbs... get a pet or tinytach to properly read your rpms

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    Sounds like the power valves are not opening to me. You need to check them first for operation of the servo motor .

  6. #6
    bex's Avatar
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    I hear the power valve servo cycle after engine shutdown and can see the cable wheel move thru its cycle on shutdown after engine flush.

    Do you recommend a full bore ride with the seat off to see if the valves move?

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    Until you get a proper tach, everything is guess work.

    Beg, borrow or steal one if you have to.

  8. #8
    bex's Avatar
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    I'll search for one of the two recommended.

  9. #9
    Moderator OsideBill's Avatar
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    The free flow exhaust, with no carb mods is a bad move

  10. #10
    bex's Avatar
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    I got you Oside Bill, sadly, I bought the ski like this in December. Will get cracking on getting the carbs out of the ski to make a decision on which way to get them up to snuff. Either send em out to you or make an attempt at rejetting and removing the TE caps myself.

    Thanks for the info, but I think the ski has a bit more left in her.

    Appreciate it.

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