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  1. #1

    GP1200R Surges at idol

    Running on the shop stand. No water (I am only running it a few seconds at a time). The engine will surge to 2400rpm and then back down to 1400 rpm (according to the PET). Compression is good across all cylinders. The things I changed were the domes (Riva heads), PV motor (bought used and seems to be working) and replaced the stinger on the PTO pipe.

    It started pretty hard. Well harder than usual. I usually just have to take the FA off the back carb and put my hand over it if I have not started it in a while. I ended up taking all three FA off and did it to each carb. It seems to start easier now but it surges. I don't know why. Any suggestions? It did not do this last time it ran in May....

    I have the pump out but I do not see why this would make a difference. I put new plugs in also just to make sure it was not a plug.


  2. #2
    PolarisNut's Avatar
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    Usually a 2 stroke surges when its lean. You sure you don't have an air leak somewhere? The hard starting issue just reinforces this possibility.

  3. #3
    Quote Originally Posted by PolarisNut View Post
    Usually a 2 stroke surges when its lean. You sure you don't have an air leak somewhere? The hard starting issue just reinforces this possibility.
    Could be possible. I will look at fuel lines. Thanks.

  4. #4
    Mike xsockguyx's Avatar
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    Quote Originally Posted by PolarisNut View Post
    Usually a 2 stroke surges when its lean. You sure you don't have an air leak somewhere? The hard starting issue just reinforces this possibility.
    If it was lean the ski would starting "running away" I would think. GPRs dont run perfectly when there out of the water. My RPM's go up down when its out of the water.

  5. #5
    PolarisNut's Avatar
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    Quote Originally Posted by xsockguyx View Post
    If it was lean the ski would starting "running away" I would think. GPRs dont run perfectly when there out of the water. My RPM's go up down when its out of the water.
    Well, surging to me is a quick, repetitive, up and down rpm...sounds like a dirt bike coming down from a long WOT run...If the engine is running correctly, it should NOT surge at idle on the trailer...idle somewhat unsteadily, maybe. All of my 2 stroke watercraft idle fairly steady at about 3000rpm out of the water. The motor has to be pretty lean to get a "runaway".

  6. #6
    Mike xsockguyx's Avatar
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    Quote Originally Posted by PolarisNut View Post
    Well, surging to me is a quick, repetitive, up and down rpm...sounds like a dirt bike coming down from a long WOT run...If the engine is running correctly, it should NOT surge at idle on the trailer...idle somewhat unsteadily, maybe. All of my 2 stroke watercraft idle fairly steady at about 3000rpm out of the water. The motor has to be pretty lean to get a "runaway".
    Nothing scarier then a lean runaway when you first have one. My GPRs RMPs are up and down out of the water but nothing crazy. In the water it runs perfectly. There was just a thread on how the GPR runs rough out of the water.

  7. #7
    Quote Originally Posted by xsockguyx View Post
    Nothing scarier then a lean runaway when you first have one. My GPRs RMPs are up and down out of the water but nothing crazy. In the water it runs perfectly. There was just a thread on how the GPR runs rough out of the water.
    I have had this since it was new back in 2000. The RPMS did move a little bit before out of the water but this is different. It is a constant surge but does not run away. It just raises RPMS and then goes back down. Sits at around 1400 for a second or so and then does it again. I have not tried it on the hose yet. I am the only one (well I had help from friends but I was always involved) who has done any work on this thing so I know how it usually runs and this is not it.

    This is a full Limited rules race boat (minus seat) with Riva Power Bomb carbs.

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Last time carbs were gone through? Pulse lines ok? Piston wash ok? Find the cause before you grenade it like I just did over a likely MF pulse line leak.

  9. #9
    Quote Originally Posted by fullboogie View Post
    Find the cause before you grenade it like I just did over a likely MF pulse line leak.

    That is why I am here asking you fine people. I just put in new rings, pistons and seals over the winter. I sure do not want to grenade it now.

    I just has the heads off and the pistons looked good. I have not done the carbs in a couple years so they are probably due. I will check my fuel lines and make sure a pulse line is not leaking or anything.

    Thanks for your help all.

  10. #10
    PolarisNut's Avatar
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    Quote Originally Posted by GPRsmartarse View Post
    That is why I am here asking you fine people. I just put in new rings, pistons and seals over the winter. I sure do not want to grenade it now.

    I just has the heads off and the pistons looked good. I have not done the carbs in a couple years so they are probably due. I will check my fuel lines and make sure a pulse line is not leaking or anything.

    Thanks for your help all.
    So did it run correctly after you rebuilt it in the winter, and just started this, or has it been running like crap since the rebuild?

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