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  1. #1

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    2001 GP1200R Carb Questions

    I just rebuilt my oem carbs. They were very clean when I opened them. Jetski had over 100 hours so it was time. Ski ran fine until I blew center piston.

    Before changing anything in carbs....

    Pop off pressure was consistent at 82 PSI
    1.2 needle and seat
    Gold 115 Gram spring
    Pilot Jet 95
    Main jet 112.5

    I put in all parts from the carb kits except the new silver colored spring.

    After rebuild, pop off pressure was still at 82 PSI.

    Question # 1 Should I be OK with everything above?

    Question # 2 below......

    Original settings....
    Carb # 1 -----> Hign was turned all the way in, Low was 1/2 turn out
    Center Carb --> High was 1 1/4 turn out, low was 1 1/2 out
    Carb # 3 -----> High was turned all the way in, Low was 1 1/2 out

    I blew the center pistion twice with the above (orignal from factory) settings. The only mod to the ski was a D-plate.

    Should I make any adjustments to the above settings?

    I am in the process of rebuilding the engine now. New crank, piston, oil block off, etc.

    Front Piston

    Center Piston

    Rear Piston
    Last edited by RetiredWW; 05-01-2009 at 09:58 PM. Reason: Pictures Added


  2. #2
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    What have you changed on the ski? stock air box? This is very importain to know, The stock air box is very restrictive and the jetting would e VERY differant if thei has been changed,
    also can you post some pics of the pistons that where in the motor?The piston wash pics would help maybe?
    do you have any reason to believe that it went lean?

  3. #3
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    Did you remove the "anti tamper caps?" the High speed and low speed adjusters should have No "T" handles on them, There should be a chunk of brass shoved down the holes where the adjusters are. You have to remove this to get to the stock screws.
    But the adjusters sound really screwed up to me. some one can give you stock setting and will I am sure.

  4. #4

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    Quote Originally Posted by great lakes gpr 1200 View Post
    What have you changed on the ski? stock air box? This is very importain to know, The stock air box is very restrictive and the jetting would e VERY differant if thei has been changed,
    also can you post some pics of the pistons that where in the motor?The piston wash pics would help maybe?
    do you have any reason to believe that it went lean?

    The only mod to the ski was a D-plate. It has a stock air box. See original post for piston pictures, I added them. I am guessing (just guessing) from looking at the pistons, that it was running lean. I wish I had checked the engine for air leaks before I took it apart, but I did not think of it at the time. I guess an air leak could have caused the engine to blow.
    Thanks for any help you can provide.

  5. #5

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    Quote Originally Posted by great lakes gpr 1200 View Post
    Did you remove the "anti tamper caps?" the High speed and low speed adjusters should have No "T" handles on them, There should be a chunk of brass shoved down the holes where the adjusters are. You have to remove this to get to the stock screws.
    But the adjusters sound really screwed up to me. some one can give you stock setting and will I am sure.
    I did remove the 'anti tamper caps' to see what the High speed and Low speed adjusters were set at. I did not replace them with "T" handles. I just put the stock screws back in. I did not want to use "T" handles because there are too many kids playing around with this ski. I don't want to make it easy for them to adjust the carb.

    Thanks for your help!

  6. #6
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    What spark plugs are in it? Should be BR8ES II gapped to .045 That hole in the center piston looks like maybe to hot of plug.??
    Have you gone threw the carbs yet? is the internal fuel filters clean? The ones on the pump side? did the gaskets look sealed? Man I have never seen a piston that beat up. It is hard to tell anything. But one of the gurus will know...

  7. #7
    Mike xsockguyx's Avatar
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    I can't even believe that was a piston at one point. But you are correct you were running very lean.

  8. #8
    Moderator OsideBill's Avatar
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    It is pretty hard to tell from the picture, that piston has run for hours after the initial failure. I did have a hole burn in the center of a piston once from a spark plug that came lose.

  9. #9

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    Can anybody comment on carb settings to start with?

    The engine seemed to be running very lean with the original settings, so I was thinking of setting all the highs at 1 1/2 turns out and all the lows at 1 turn out. And then tune down from there. Seems better to start rich and avoid damage from running too lean.

    1. Am I right????
    2. Is this a good approach?
    3. Can I cause damage by running to rich?

  10. #10

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    that is a good starting point, running rich is far better than lean

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