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  1. #1
    ajharbin's Avatar
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    Need Help ASAP PLEASE!

    Well guys I seem to be having a problem with my Gp1200r. When I bought the ski the center cylinder had been fried looked to be leaned out. So I went ahead and rebuilt the the whole top end and carbs. The problem popped its head back up again with another center piston getting fried. So my question is are my carbs running to lean I do have some mods done to the ski ( stock head that has been milled running 160PSI compression, riva s2 stinger, free flow exhaust, solas impeller, PPK and wave eater clips). If the carbs need to be rejetted what jet size do I need to go to? Any help would be greatly appreciated.
    Thanks,
    AJ.


  2. #2
    Happily Self-Employed WFO's Avatar
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    what all did you replace and what brand parts used?

    did you pressure test the engine after assembly?

    pics of damage?

    yes carbs need to be updated on jetting, especially if you are running a high compression head

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  4. #3
    ajharbin's Avatar
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    Click image for larger version. 

Name:	IMG_9653.jpeg 
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ID:	323895Heres the Piston. It is the center cylinder, when I bought the ski it had the same problem with the center cylinder being fried.

  5. #4
    wotxxxsd's Avatar
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    Yeah that's torched..

  6. #5
    Happily Self-Employed WFO's Avatar
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    ouch

    I would recommend getting the crank out and send it off to be checked... with that amount of damage (and being its the second time) the bearings are going to have debris in them

  7. #6
    Fat Man, Little Boat Region8Ultra250X's Avatar
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    what the others have said... you should have rejetted when you did the mods the first time....

  8. #7
    hammer5312's Avatar
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    From having had two stroke motorcycles....
    any time you make a change to the exhaust, you are going to have to watch your jetting on the intake. Since two strokes are lubricated with the intake charge it is more critical to watch jetting than four strokes....
    If she is breathing better with a pipe she is gonna be lean....

  9. #8
    ajharbin's Avatar
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    Ok so I did some digging and found an old thread where Bill had posted some jetting for a gp1200r with F/A installed. The settings were:
    1200R Aftermarket F/A's (Flame Arrestors) chokes intact

      • 110 Pilot jets, 1 turn out on low speed adjusters
      • 120 main jets, 1-1/2 turn out on high speed adjusters
      • 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure
    Will this jetting be enough with the mods I have the only thing ill have to get would be some F/A if anyone has some for sale?? let me know please...Thanks again for all the feedback.

  10. #9
    bscpaint's Avatar
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    Stupid question but are you still running an oil pump?

  11. #10
    ajharbin's Avatar
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    Yes I am with the long distance riding I do its not feasible to run premix. planing a trip now to ride down the Chattahoochee from Columbus,GA to Panama City Beach,Fl in one day theres going to be about 8-10 of us on skis.

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