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  1. #1

    gp1200 engine blown why?!?!

    Well I have a 1998 gp1200 with a head. Other than that it is completely stock engine wise.

    Anyways, rebuilt it and just got done breaking it in. My mom was out on it and said she heard a popping sound. So she brings it in and tells my dad who then goes out on it to see what shes talking about, he can't get the ski to go over 40 mph and brings it in and pulls the seat. No compression in the front and rear cylinder and blown rear seal.

    Just tore the engine down and looks like detonation to me. Any ideas on what caused this???

    also, the rear cylinder appeared to have water in it.
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  2. #2
    Adam's Avatar
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    Wink

    Fuel pumps in the carbs need overhauling ! It is the main cause of this type of damage on GP1200 engines. Do a search on these forums and you will find heaps of information about it. Carbs should be checked every 12mths to prevent damage occuring.

  3. #3
    Carbs and fuel pumps were rebuilt at the same time as the engine

  4. #4
    YudLuz2's Avatar
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    Stock jetting with a head mod?

  5. #5
    yes but it didn't appear to be running rich or lean

  6. #6
    YudLuz2's Avatar
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    And you don't think its lean with a hole in each piston
    You need to rejet anytime you add this type of mod.

  7. #7
    why would the front and rear go but not the middle one then? Also how would that explain the possible water in the rear cylinder and the seal blowing out?

  8. #8
    YudLuz2's Avatar
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    Some cylinders run hotter than others, and need more fuel.
    You have so much damage and heat you could even have a cracked
    head. When you say seal, do you mean the head gasket? Or crank seal?
    Why did you need to rebuild it the first time? And what psi head are you running?

  9. #9
    Flying Scotsman's Avatar
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    Wow you destroyed that motor
    Did you do a leak down test ?
    You need to take a good look at the crank it most likely is shot too.
    Go through the carbs and post pics.
    Oh and tumblingtwerp9 you would be advised to listen to YudLuz2 he knows what hes talking about.

  10. #10
    Adam's Avatar
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    I would still check the fuel pumps, its been very lean to melt the pistons so much. What jetting are you running and what fuel and how high was the compression ( head volume in cc"s) ?

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