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  1. #1

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    Post 99 GP1200 stalls on hard turns

    I bought a used 99 GP1200. When I got it out on the water, I noticed that it would not accelerate past 40mph. Not knowing its history, I thought that it would be good time to rebuild the carbs. I stripped down the three carbs, cleaned them, and then rebuilt with kits. This solved the acceleration issue.

    The ski runs good (idles fine - responds well to a hard acceleration). However, when I make a hard turn (either direction) the ski will stall. After I complete the turn, the ski begins to lose RPMs. If I act quickly and pop out the choke, the ski will recover. I only need to pop out the choke for a second and then pop it back in.

    Iím stumped. Any ideas on what may be causing this problem?


  2. #2

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    I'm not sure if this is related, but this ski needs to be choked to restart after it has been off for 30sec. My other gp1200 only needs to be choked initially, and will restart all day without choke.

  3. #3
    slothman's Avatar
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    Quote Originally Posted by mtech View Post
    I'm not sure if this is related, but this ski needs to be choked to restart after it has been off for 30sec. My other gp1200 only needs to be choked initially, and will restart all day without choke.
    It is most likely starving for fuel, due to the fact that you have to choke it to keep it running. When you rebuilt the carbs, did you check the pop-off pressure?

    I would also inspect all of the fuel lines and make sure they aren't pinched or blocked (especially while turning the handlebars)

  4. #4

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    Thanks for the reply. When I rebuilt the carbs, I did not have a pop-off pressure tester. I think I will need to buy one.

    My setup is currently stock. Yamaha service manual states that the carb has a 1.5 valve seat. I could have swore when I took it apart that the valve seat read 1.2. The spring I took out was dull silver, so I put in new dull silver springs from the kits. The pop off chart in the Mikuni manual does not list 1.2, but based on the values for other seats, I estimate a 1.2 seat with a dull silver spring to have a 65 psi pop off. Many people say the pop off on a stock configuration is too high. Any recommendations?

    All the fuel lines seem to be clear of obstructions while turning the handle bars. They appear to be the original lines... its probably time to change them.

  5. #5
    CHICKA WAH WAH bren's Avatar
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    little flap door on the fuel pick up in the tank.
    they deform / bend / close over in hard turns.

  6. #6
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by mtech View Post
    Thanks for the reply. When I rebuilt the carbs, I did not have a pop-off pressure tester. I think I will need to buy one.

    My setup is currently stock. Yamaha service manual states that the carb has a 1.5 valve seat. I could have swore when I took it apart that the valve seat read 1.2. The spring I took out was dull silver, so I put in new dull silver springs from the kits. The pop off chart in the Mikuni manual does not list 1.2, but based on the values for other seats, I estimate a 1.2 seat with a dull silver spring to have a 65 psi pop off. Many people say the pop off on a stock configuration is too high. Any recommendations?

    All the fuel lines seem to be clear of obstructions while turning the handle bars. They appear to be the original lines... its probably time to change them.
    yes the stock one is 1.2

  7. #7

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    Bren, good suggestion. I took mine apart and found a bent flap. I replaced it with a spare I had. I hope to get out on the water in the next few days to test everything out. Thanks!

  8. #8
    old school big raider's Avatar
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    make sure youve got good pressure in your tank -could be as simple as bad gas cap or losing fuel pressure along the circuit thats why its starving in turns and on start up no fuel in lines its getting dumped back into tank thats why you have to prime- may want to put a restrictor in return line-i think i have a riva restrictor that you screw a jet into to keep fuel lines pressurized if you want it

  9. #9

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    I took my ski out yesterday. It is still stalling on turns. I never mentioned this before, but it will also start to die if I "pump" the throttle (hard throttle... back off.... hard throttle). It will, however, get up to full speed if I give it full throttle without backing off. I can even go WOT from a standstill and it will blast off fine. I'm not sure if this is related to it dying on turns, but it also seems like a lean condition as I need to choke to recover.

    I've replaced the flap at the bottom of the fuel tank. I've also replaced the packing (gasket) on the fuel cap as the old one was shot. It now lets out a nice "puff" when I open the cap.

    Should I go out and buy a pop off tester? If one carb was out of spec, would it cause the whole thing to die? Or is my problem external to the carbs?

  10. #10

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    It's the start of another season. I've made many changes, but have not been successful in resolving this problem.

    I need to revise the description of my problem. After looking at things with fresh eyes this season, the problem is not caused by a turn. I tend to let off the accelerator on a turn and then accelerate after the turn is complete. If I hold the throttle steady, the boat won’t die.

    So my issue is that the boat will die if I give a moderate to hard acceleration from idle. If the boat is a little above idle when I do this, everything works fine. New for this season, the boat will occasionally die if I’m running 1/2 throttle for an extended time. The only way to recover from this issue is to close the choke for a split second and all will be fine. I got to be quick though, as too much choke will also cause it to become rich and die.

    If the boat sits for a few min or more, I always need to pull the choke to restart.

    I bought a pop off tester and found pop off to be 60psi for the three carbs. This was difficult to test as I kept blowing off the plugs I devised to plug the return lines for the test. I am running with the stock airbox / flame arrestor.

    During the pop off test, I discovered that the middle carb was leaking through the cover gasket. As a result, I stripped this carb and then rebuilt it.

    Other things I’ve tried without success:
    Changed fuel filter
    Changed fuel lines
    Changed check valve
    Opened low speed screws 1/4 turn

    I’m really stumped. I’ve lost sleep last night as I was running through my head the next thing to try. Any ideas will be greatly appreciated.

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