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Thread: gpr800 head

  1. #1
    yz450f's Avatar
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    gpr800 head

    ok i got my hands on a set fo 1200 riva rec heads. they bolt up and fit but i have a few questions
    1 has anyone ever ran 1200 heads on a 800? the 800 and 1200 use the same size piston so shouldnt this fit???

    any info on these heads at all would be helpfull
    thank you
    Last edited by yz450f; 01-28-2009 at 08:25 PM.


  2. #2
    Moderator beerdart's Avatar
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    Hey YZ you have a build thread why dont you ask all your questions in that thread instead of starting a new thread for every question. Keep it all in one thread that way we can keep track of your build.. 2 cents.

  3. #3
    yz450f's Avatar
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    i try but not many people look on my build thread.
    but ok ill do that from now on.

  4. #4
    yz450f's Avatar
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    we still havent come up with a good answer
    the 1200 and 800 have same size piston
    here is a pic
    anyone tried this before??
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  5. #5
    Randy11023's Avatar
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    As i recall the piston in a 800 is 80mm and a piston in a 1200 is 84m

    But not 100% sure.

    Randy

  6. #6
    billy's gpr's Avatar
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    800 and 1200 are 80mm bore ,1300 are 84mm,1390 are 87mm ,thay all run the same 78mm stroke !!!!!!!!!!!! standard that is!!!!!!!

  7. #7
    yz450f's Avatar
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    Quote Originally Posted by billy's gpr View Post
    800 and 1200 are 80mm bore ,1300 are 84mm,1390 are 87mm ,thay all run the same 78mm stroke !!!!!!!!!!!! standard that is!!!!!!!
    i think im gonna try them
    im going to tighten them down and see if it turn over smoothly
    the motor is on the bench soill hear if anything sounds bad

  8. #8
    yz450f's Avatar
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    i tried them and after torqing them down i slowly turned it over and it sounded normal
    then i put in the spark plugs and still normal
    i took them off and there was a ring around the head like the outside so im not even gonna bother
    800 motors need 800 heads plain and simple
    but im going to milll my stock head un less anyone has a cheap head for sale for a gpr800 66e motor

  9. #9
    Randy11023's Avatar
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    Look in to the group-k they have a kit for about 500. Subpose to help all around proformance. Maybe be cheeper if you have some of the kit already.

    http://www.groupk.com/y800gp.htm

    Randy

    PS: My 1998 gp1200 says 84mm I also found this info

    This is a WSM Yamaha 1200 GP high performance piston kit - Kit includes rings, pins and clips.

    size available:STD 84mm

  10. #10
    yz450f's Avatar
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    Quote Originally Posted by Randy11023 View Post
    Look in to the group-k they have a kit for about 500. Subpose to help all around proformance. Maybe be cheeper if you have some of the kit already.

    http://www.groupk.com/y800gp.htm

    Randy

    PS: My 1998 gp1200 says 84mm I also found this info

    This is a WSM Yamaha 1200 GP high performance piston kit - Kit includes rings, pins and clips.

    size available:STD 84mm

    nice link man

    but i think im doing about all those mods except the bore and im going to have my crarbs modded by carl at island.

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