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  1. #1

    97 GP1200 Trouble with Dribbles

    I purchased a 97 GP1200 late last year that had low compression in the PTO cylinder. I rebuilt the engine over the winter. I got everything back together and I am trying to get the carbs to stop dribbling.

    I rebuilt the carbs with genuine Mikuni kits. I purchase 3 new 1.5 N&S. I first used the heaviest spring in the kit and was getting 52 psi pop off on all three carbs. I incorporated O Side Bill’s fuel return mod and I am getting 1.5 psi in the return line at idle. I put everything together and all 3 carbs would dribble like crazy. I did double up the flapper valve that is on the block that covers the jets.

    I wasn't sure what gram springs came with the kits so I ordered 3 gold 115 springs and installed them. I now have 60 psi pop off and the carbs are still dribbling and running horribly rich.

    The carbs originally looked like they have never been taken apart. There were no marks or paint chipped off any of the screws and they had 1.2 N&S installed.

    So I guess my only option is to order some new 1.2 needle and seats and try and get the pop off even higher?

    I have searched high and low for solutions and found mostly suggestions nothing definitive on fixing this problem. I have only ran the engine on the hose in the back yard.

    Here is what I have done to the engine:
    Sent cylinders to Full Bore Online in Michigan for boring and new pistons rings and complete top end kit.
    All new OEM crank seals
    Crankshaft and rods were in good condition.
    Performed successful leak down test before installing the engine.

    Any help would be appreciated.

    Last edited by bstewart63; 05-11-2013 at 12:41 PM.

  2. #2
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    The definitive thread on GP1200 carb dribble is this one listed below. It may go away after some break in riding in the water. But pay special attention to the_natrix's posts in this thread. Thats the solution if all else fails.

  3. #3
    Thanks Cutlass that is some good information. I didn't mic the bore and pistons but they felt pretty snug. I guess I will go ahead and run it a while and see what happens.

    Thanks again.


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