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  1. #1
    TuningForkMarine's Avatar
    Join Date
    May 2013
    Palm coast FL / Shakopee MN

    Milling stock head on GP1300R

    hey guys wondering how much to take off on a stock GP13R head to bring compression to 150 ?? head is at the shop, i wanna make sure the machinist knows exactly how much to skim off

  2. #2
    KaFF's Avatar
    Join Date
    Aug 2008
    Miami, FL
    Send your Head to Jims Performance. give it to some one with experience, as you also need to cut the squish. you also need to know what your base compression is now to see if your rings are good, and how many hrs does the motor has. lots of factors before you start moding. good luck

  3. #3
    The lip on the head is somewhere in the .040 range, and that's all you'll be able to take off. As been said, to get 150psi you'll have to take more like a total of .080 + but you will be eating into the squish band in the head dome, which in turn will require a machinist to modify the band angle etc.. He has to know what he's doing to do that aspect of it. (Some local machinist' do; some don't.) Otherwise just cutting .040 will give you about a 15psi bump thereabouts.

  4. #4
    OzarkYamMonster's Avatar
    Join Date
    Oct 2012
    Lake Of The Ozarks
    I sent my heads off to Jim's performance he cut them & sent back all in a weeks time. I Pressure check right on @ 150psi ......... best part the work only cost $85.00 + SHIPPING.
    Best $100 I ever spent so far on this ski

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