Gp1200r running bad

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  1. #1 Is My Home Away From Home Myself's Avatar
    Join Date
    Jun 2006

    Gp1200r running bad

    So this Gpr is hard to start and falls on it's face when given the throttle. This is the second time I've pulled that huge stupid exhaust off. I've cleaned the carbs to a shine and replaced the little vacuum hoses in between. Am I not getting them clean enough??? They look VERY clean to me. Any suggestions would be great.
    Attached Images Attached Images

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  2. #2 Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Riverside, CA
    Blog Entries

    Re: Gp1200r running bad

    Did you inspect the fuel pump check valves for being dished (compressed),
    and for a pin hole in the fuel pump diaphragm. As I remember it was a
    problem on Yamaha 44's, but my tech update book doesn't specify SBN, or
    SBN-i carbs.

    I read somewhere that you have a flat plate set up for flat sanding?

    Besides inspecting the reeds, I would assume that carbs with an accelerator
    pump would be more sensitive to vacuum leaks than carbs without an
    accelerator pump.

    The problem is made worse when the oem gaskets are reused. On Yamaha's
    I don't trust any part of the intake manifold to be flat. I used to inspect all
    3 carb bases, the carb adapter, the intake manifold, and I used to flat sand
    reed cage too.

    I had good luck with flat sanding all the intake pieces and replacing all the gaskets.

    I would also assume the stock low screw settings are now obsolete. The book lists
    the setting as 1 +/- 1/4 turn.

    Bill M.
    Last edited by wmazz; 07-05-2019 at 02:56 AM.
    Horsepower == Speed, RPM != Speed

  3. #3
    Resident Guru
    Join Date
    Sep 2015
    Northern Michigan

    Re: Gp1200r running bad

    Pulse line and fitting?

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