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  1. #1
    Crazy rider seeking waves. CustomGP800's Avatar
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    99 GP800 Compression/Head?

    I own a 99 GP800 and if i am correct, the stock compression is around 6.6:1, which is somewhere around 100psi? Can i mill the stock head to get me somewhere around 8:1 compression? Will I have to take off too much material? I dont want to switch to high octane fuel. I shouldnt have to switch fuel until i get around 9:1. I just want to get the most out of my pump gas for cheap. ANY input would be greatly appreciated!


  2. #2
    You stock head should be 120 psi. I have a pro-tec rec head in mint condition with removable domes for sale. I am looking for 350 for the head and domes shipped.
    What ever you may do you will need to re-jet the carbs. This head with the domes I have will bring the compression up to 135 psi which really wakes up the ski and you can still run 87 octane as the compression isn't that high.
    PM me if your interested

  3. #3
    Crazy rider seeking waves. CustomGP800's Avatar
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    I really didnt want to spend that much. I know a guy with a machine shop that will mill my head for me, but I was wondering if thats something i could even do.

  4. #4
    you can definitly mill the head but I do not know off hand what the mill specs are. The other benefit of the pro tec head is that if you blow a cylinder all you change it the damaged dome. if you use a OEM head and the cylinder goes you just lost you whole investment of the milled head.
    Contact Lowell Horning, he can mill you head to what ever compression that you need!
    His website is www.2-stroke-porting.com I know he is in the process of moving so bare with him if he doesn't back to you right away, but he is the man if you want yours milled!!!!!

  5. #5
    Crazy rider seeking waves. CustomGP800's Avatar
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    Do you think if i contact him he could just give me the mill specs? I work at an engineering firm with bookoo tools. If i had to i could chuck the head up in our CNC machine.

  6. #6
    I dont know if he only mills the tops, he may alter the squish bands as well. Thats something you would have to as him.

  7. #7
    Crazy rider seeking waves. CustomGP800's Avatar
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    Thnx!

  8. #8
    jdog800's Avatar
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    150 psi is pump gas safe. Anything over that requires race fuel. You can deck the heads without changing squish angles to get there. Another easier trick is to take the middle section out of the 3 piece head gasket. You can gain some compression without the cutting.

  9. #9

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    i have a stock head already milled that will bring you close to the 150 mark ( not 100% sure of psi) been awhile since i ran it. very clean no pit marks

    $ 100 shipped.

    pat

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