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Thread: Missing RPM???

  1. #1

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    Missing RPM???

    Hi all, New to the board but I've been reading all the boards for the last two years. I've learned a bunch just reading all the post! Now my question.

    I got a 01 GPR with 104 hours on the clock. Mods are PPK, R&D intake grate, Riva plate, Jet works mod, Jetted carbs, flame arresters with socks, D-plate.
    I installed a IR 12/19 nuget before I rejetted the carbs and was turning 6950, this was last october. I rejetted the carbs over the winter thinking it would get the rpm back up. Went out friday and rpm was only 6980. Came out a 1/4 turn on the highs and got it up to 7120. I was happy with that. GPSed 66.4. High screws are now 1.5 turns out.
    Went back out today, ran good all day wasn't really paying attention to the tach and such just riding letting the tank get low. Tried a couple of runs but was only getting 6860 at 64.2. Pulled the seat and made sure the PV's were opening. Came home did a compression test, got 125 on all three holes just like it's always had. Plugs have a nice brown color to them.
    Do the flywheel keyways ever start to shear and retard the timing on these. At about 90 hours I got this vibration, So pulled the motor and found the flywheel bolt kinda loose, like it barely had about 10 ft lbs of torque on it. I just loctited it and retorqued it. I didn't remove the flywheel! Vibration went away after this.

    Brian


  2. #2
    ABBOTT's Avatar
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    Welcome to the forum.

  3. #3
    Moderator RX951's Avatar
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    Welcome to the Forum Brian

  4. #4

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    Thanks for the Welcome!

    I guess nobody had any ideas? I thinking maybe the prop is to steap on the top end. Only thing that gets me is that it screams out of the hole and in the midrange.

  5. #5
    Hypertoys's Avatar
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    Do you have the waveeater clips ,I have had the pin to come out of the PV and the PV would close ,but shaft still moves.

  6. #6

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    I don't have the waveeater's. But I do check them every 5-10 hours. I got rid of the stock shaft couplers many hours ago, used 5/16 double braided hose and clamps.

  7. #7
    Hypertoys's Avatar
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    the pin on the PV will slide out

  8. #8

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    Just got done checking them, everything still looks brand new. I'll probably go ahead and pull the flywheel tomorrow. Even if there is nothing wrong there I'll go ahead and install a 4 degree key.

  9. #9
    IMO 4 degrees is too much for that engine. I would recommend going with an Advent. I know of someone who seized after installing a 4 degree on a 1200 engine.

    For the 1200 the Advent Ignition is the best option. Ben Herman is running one of my 3 degree keys on his 1200 with success, but he is the only one.

  10. #10
    spud's Avatar
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    What did you rejet your carb to? with F/A's you should be running 110 lows 120 highs 1.5 N&S with a black or gold spring. Your high speed screws should be 1 1/4 to 1 1/2 and your low speed screws should be 7/8 to 1 turn. Your accellerator pump should be disabled. Those numbers are for choke plates in. I have heard 125 mains with the choke plates out.

    Your impeller doesn't sound too steep if that is the true pitch. A Solas 13/19 is the best for a stock compression engine. Get your head milled at Pro-Tec or Riva and make sure your carbs are jetted properly.

    It sounded odd that you turned your high screws out and your rpm's went up. You could be running it too lean.

    There also may be something to your flywheel key.

    A 2 degree key would be perfect for the GP1200R's (FERCHO). The 3 degree key mimics the old stinger 2 YAM 59 curve except around 4700 rpms where it is 1-2 degrees more advanced.

    3 degrees sounds like mixing in race gas and increased jetting to avoid deto.

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