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  1. #1
    I wanna go FAAAAASTer!! CDW78's Avatar
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    97 Gp1200 Engine Rebuild

    Guess I shoulda posted it here to begin with... Been a while since I've been on - forgive me

    Ok, long story short -
    Im guessing the carbs were stopped up and caused the hesitation with it not wanting to take the gas unless I took it easy on it and then it was fine during end of season last year.... It set all winter, so it probably made it worse. But I dont know for sure what the problem was. for sure!
    Either way, the 3rd piston is blown ( been replaced with an SBT before @ 75hrs )
    The cylinder wall is scared up a little. The piston will def need to be replaced and the head has some minor scratches/scaring on it from the lose pieces. Everything still moves up and down fine, so thats def. good, I suppose.
    I am just wondering what are my best options from here? I do want to be cost effective, but dont want too be cheap eiter and end up causing more damage later!

    Heres a link to the original thread incase -
    http://www.greenhulk.net/forums/show...e-blown-engine
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  2. #2
    kodez's Avatar
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    I am in the same situation so ill tell you what i have done so far. Lost my number three piston due to metal fatigue. Bored cylinder slightly, just enough to remove the light scratches prolly only .008". Ordered ProX pistons, new gaskets, found a couple of high compression heads, and found an old riva cdi. I'm still waiting on my gaskets to show up, once they do the engine will be back together. I am also in the process of reworking the carbs as well, im installing the triple primer kit, pulling the choke plates out and general cleaning.

  3. #3
    krispaintballz's Avatar
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    Quote Originally Posted by CDW78 View Post
    Guess I shoulda posted it here to begin with... Been a while since I've been on - forgive me

    Ok, long story short -
    Im guessing the carbs were stopped up and caused the hesitation with it not wanting to take the gas unless I took it easy on it and then it was fine during end of season last year.... It set all winter, so it probably made it worse. But I dont know for sure what the problem was. for sure!
    Either way, the 3rd piston is blown ( been replaced with an SBT before @ 75hrs )
    The cylinder wall is scared up a little. The piston will def need to be replaced and the head has some minor scratches/scaring on it from the lose pieces. Everything still moves up and down fine, so thats def. good, I suppose.
    I am just wondering what are my best options from here? I do want to be cost effective, but dont want too be cheap eiter and end up causing more damage later!

    Heres a link to the original thread incase -
    http://www.greenhulk.net/forums/show...e-blown-engine
    Get it all ripped apart. If the crank is good go .25 or .5 over and run either wiseco top end or pro-x. They are both owned by the same company. If you go with wiseco go .007 clearance and if you go pro-x go .005 clearance.

    Quote Originally Posted by kodez View Post
    I am in the same situation so ill tell you what i have done so far. Lost my number three piston due to metal fatigue. Bored cylinder slightly, just enough to remove the light scratches prolly only .008". Ordered ProX pistons, new gaskets, found a couple of high compression heads, and found an old riva cdi. I'm still waiting on my gaskets to show up, once they do the engine will be back together. I am also in the process of reworking the carbs as well, im installing the triple primer kit, pulling the choke plates out and general cleaning.

    Do it right, go .25 or .50 over if you are over clearance. .008 is a bit for the pro-x, not saying it cant be done. Be sure to stay within size of the other to pistons or you will have crank failure soon.

  4. #4
    I wanna go FAAAAASTer!! CDW78's Avatar
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    Thanks for the info. I figured a new top end was needed, but wasnt sure if all 3 pistons needed to be replace or just the one ?
    I've priced the WSM platinum top end kit for $320 shipped, bore and hone all 3 for $75. But replacing one is a bit cheaper than all 3 as well..... will NEW gasket be needed for sure?
    The head is also an issue? How would I know if the crank is good or bad ( other than the obvious things, like bearings out, etc ) ???
    Thanks again!

  5. #5
    Yamaha artisan Cutlass's Avatar
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    You have to take the crank out, look it over, spin all the bearings. If the bearings spin smoothly, you're probably ok. If they have a gritty feeling or rough spots then they'll need attention.

    Maybe this eBay auction can help you out.
    GP1200 top end

  6. #6
    kodez's Avatar
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    Do it right, go .25 or .50 over if you are over clearance. .008 is a bit for the pro-x, not saying it cant be done. Be sure to stay within size of the other to pistons or you will have crank failure soon.[/QUOTE]

    Thank you for the advise. I'll check clearances again. What are the tolerances to stay within the other pistons to prevent crank failure.

  7. #7
    krispaintballz's Avatar
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    Quote Originally Posted by kodez View Post
    Do it right, go .25 or .50 over if you are over clearance. .008 is a bit for the pro-x, not saying it cant be done. Be sure to stay within size of the other to pistons or you will have crank failure soon.

    Thank you for the advise. I'll check clearances again. What are the tolerances to stay within the other pistons to prevent crank failure.

    I dont use wsm. I stick with pro-x, Wiseco, or ART.
    I always say .005 - .0055 on a cast piston, and .007 on a forged piston for the 65u.

  8. #8
    kodez's Avatar
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    Quote Originally Posted by krispaintballz View Post
    Thank you for the advise. I'll check clearances again. What are the tolerances to stay within the other pistons to prevent crank failure.

    I dont use wsm. I stick with pro-x, Wiseco, or ART.
    I always say .005 - .0055 on a cast piston, and .007 on a forged piston for the 65u.
    Ok thanks

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