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  1. #1

    GP800 popoff pressure?

    I am rebuilding the carbs on a 2000 GP800 ski and am at the point where I need to set the popoff pressure. Before I took the carbs apart the ski ran fine, except it was hard to start when cold. Actually, it has been hard to start cold ever since we bought it back in 2000. From searching, I saw that the stock popoff pressure is 75+psi and that a popoff pressure that high can be a cause of hard starting.

    My question: Will I have any issues if I lower the popoff pressure to 50-55psi? The ski and motor are still completely stock.

    Thanks,
    Ryan


  2. #2
    Yamaha artisan Cutlass's Avatar
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    If the ski is completely stock, then generally the stock Pop-off pressure is recommended. Its is safe to experiment with lower pop-off pressures if you want since lower pop-off will richen up the off idle -1/4 throttle fuel ratio.
    A better solution for your hard starting would be to install a primer kit, instead of a choke. If you go that route, plumb it into the return line, not the "on" or "reserve" line like alot of instructions say.

  3. #3
    Budman's Avatar
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    My pop off is set at 30 as instructed by tim judge. But maybe its only for ported engines.

  4. #4
    Budman's Avatar
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    Quote Originally Posted by Cutlass View Post
    If the ski is completely stock, then generally the stock Pop-off pressure is recommended. Its is safe to experiment with lower pop-off pressures if you want since lower pop-off will richen up the off idle -1/4 throttle fuel ratio.
    A better solution for your hard starting would be to install a primer kit, instead of a choke. If you go that route, plumb it into the return line, not the "on" or "reserve" line like alot of instructions say.
    Mine is T'ed into the reserve line. I thought is I T'ed into the return line it would suck air from the fuel tank. Does it draw fuel through the carbs and to the primer?

  5. #5
    Yamaha artisan Cutlass's Avatar
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    The carbs suck the fuel out of the tank and with the tee in the reserve line, it could suck air also...when you use reserve. Plus the tee restricts fuel flow.
    Yes in the return line, the primer sucks fuel through the carbs. Also alot of people run a longer return hose so it has a big, low loop in it. then they put the tee in the lowest part of the loop so hopefully there will be plenty of gas sitting there for the primer to pump.

  6. #6
    So if you plumb the primer into the return line, I'm assuming you also have to reverse the lines on the primer? That way your inlet side would draw fuel through the carb through the return line, and then push any air/fuel into the tank instead?

  7. #7
    Yamaha artisan Cutlass's Avatar
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    I'm not sure what you're asking. There's only 2 lines on the primer. one line sucks fuel into the primer pump and one line pumps out from the pump towards the top of the carbs.

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