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  1. #1

    GP1200R Backfire...Help Please

    Okay so summary of what's been done to my 01GP1200R.

    Carbs Replaced (purchased from Duke who went through them)
    D Plate
    Flame Arrestors
    Jet Works
    Solas Prop 13/19
    Primer Kit
    Dual Fuel to Carbs

    Everything was put back together and started it up. Problem at first was a loud backfire when it started up and then also when throttle was hit. Idle was also low so we adjusted that. Let it run for a bit and then shut it down and started it back up, again got a loud backfire.

    Couple of questions, how should the t adjusters be set? Could this be a gas problem or filter? Live in MA so it was about 50 degrees out, could that have anything to do with it? Help please... BTW This forum has helped me sooooo much and big thanks to Paul C, WFO, Duke, Osidebill and everyone else for all the help with my ski! Keep the info coming.

  2. #2
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Minden, Nevada, United States
    Have you checked the reeds?

  3. #3
    Ya checked the reeds before it was put away and they looked okay

  4. #4
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    What are the carbs jetted to right now? you probably already told me but I forgot. they should be 110 low, 120 high, 1.5 N&S, 95Gr spring, 1 turn out on the low speed screw, and 1.5 on highs.

    Backfire usually means there is an air leak somewhere, so check carb rack to reed cover plate gasket, this is a known leak area.

  5. #5
    paul c's Avatar
    Join Date
    Sep 2008
    chris' ski also has the chokes removed so they should have 125 on the main jets, correct? the lows were set to 3/4 out so perhaps that may be some of the issue. this ski was put through hell by it's previous owner, chris is trying to get it back up to par.

  6. #6
    Update....Okay so I'm still waiting to hear back from Duke on what these were jetted to.

    Today I set the low speed back two screws to 1 turn out, (HELP on getting to the front one...Any suggestions??) and the Highs are all at 1.5 turns.

    My Backfire (LOUD POP) Noise is happening when you let the ski idle for a bit and then turn it off, as soon as you start it up you get the LOUD POP.

    When I initially started it, I actually did not get any pop, only when I shut it down and then started it back up. Just out of curiosity, could this be because for some reason there is no fuel when I'm starting it back up. When I first start it I use the primer but then I do not, Should I be using it every single time?

    Hope this helps...and hopefully you can help me...

  7. #7
    paul c's Avatar
    Join Date
    Sep 2008
    a back fire could possibly be from excess fuel. did you get to run it on that lake? i wonder if the timing was ever messed with?

  8. #8
    Hey Paul, sorry for not getting back to you, just got in the house, No I actually did not get to run it today, got late after making the adjustments and changing the fuel filter.... What to do next??

  9. #9
    Just heard back from Duke, the carbs were jetted to 125m and 110p . Any suggestions? What ya got Osidebill, Your a pro at this stuff.... THANKS EVERYONE

  10. #10
    Sounds like you may be getting too much fuel. Are your plugs wet after you run it? Are you sure all your plugs are firing? It could be idling on two cylinders and then back fire when you restart. Did you check you pulse line hoses to make sure you did not have a crack in one.

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