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  1. #1

    gp1200r head questions

    What's up guys I tried searching for answers but couldn't find what I needed. I have a 01 gp1200r. Performance wise I have. 13/19 prop, riva intake grate, riva ride plate, free flow exhaust, d-plate with sensor, rival flame arrestors, carbontech reeds. Next I wanna do a head. I want to keep my stock head and mill it. My friends dad owns a machine shop. I found I need to get each head to 37cc than the gasket will bring it to 41cc for the psi to be between 140-150. Ill be running 92-93 octane with this setup. My question is how much in thousands do I tell him to mill tgw heads. Any input is incouraged. Any other suggestions of what else to do performance wise is good also. Are there any spark plugs you would recommended over the ngks they call for?


  2. #2
    slothman's Avatar
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    Be careful with high compression heads....you could pop those pistons REAL easy. I would run NGKs two steps colder than the stockers to prevent detonation.

  3. #3
    thats the same compression that the riva stages offer. if its the unreliable would they offer it in the stage 1 and stage 2 kits? i dont know thats why im asking. ive read that aftermarket heads the o-rings dont seat well and another option is mil the stock head which a lot of people are doing so im reading

  4. #4

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    Its not just as easy to mill the head. You can only mill it so far before cutting into the squish band, if you start cutting in the squish band (angled part) then the round dome starts getting smaller.

    You can mill just the step off, but not go into the squish band and you should get it into the 120-130 psi range, that along with using only one layer of head gasket. This is a good mod for the money. I've done several this way.

    Other option is to send to someone that can cut the squish band correctly with correct angle and mill the head to get to 140-150psi.

  5. #5
    thanks ronn! this in the kind of info i was looking for. i didnt know about the squish band or cutting into the dome. you by and chance dont have a picture for reference do you? i dont wanna get myself into anything that will cause me problems down the line. but than again i am changing compression lol. so might keep it at 120-130 range.

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    I don't have pic of it. On a 1200 head from what I remember you can only cut very little before getting into the chamber. Run your finger across it and feel the lip, I think its only .010-.015" from what I remember. The compression increase mainly comes from removing 2 layers of the head gasket. Free mod. If you can get it lightly surfaced or milled slightly for cheap then go for it.

    On a 1300 the lip is much bigger.

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    WATER WOODY's Avatar
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    Most important! have you rejetted your carbs? If so, what jetting and what was done. DO NOT run the ski with the FA's on stock carbs.

    Welcome to the forum

  8. #8
    slothman's Avatar
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    Quote Originally Posted by WATER WOODY View Post
    Most important! have you rejetted your carbs? If so, what jetting and what was done. DO NOT run the ski with the FA's on stock carbs.

    Welcome to the forum
    ^^yep

    no rejet = lean = engine BOOM

  9. #9
    PolarisNut's Avatar
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    Quote Originally Posted by surfnaked2010 View Post
    thanks ronn! this in the kind of info i was looking for. i didnt know about the squish band or cutting into the dome. you by and chance dont have a picture for reference do you? i dont wanna get myself into anything that will cause me problems down the line. but than again i am changing compression lol. so might keep it at 120-130 range.
    Send your head to OsideBill...He'll do exactly what you need. With stock exhaust port height, 150psi is PLENTY safe w/ 92oct. You definitely want the squish band reconfigured. You still have to remove at least one layer of head gasket to get the squish tight though. The best way to do it is to also deck the cylinders so you can run a stock head gasket, but that gets pretty involved, and pricey.

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