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  1. #1

    1200r piston advice

    Ok here is what i have. One good cylinder stamped # 8 with a cylinder bore reading of 3.1502 in. or 80.015 mm. My queation is what size and brand of piston to order? The size the cylinder # 8 calls for? and end up with 4.3 thousandths clearance? or order the next size bigger pistons? Going to have the two bad cylinders replated to fit new pistons. The other question was what brand to order? prox? or oem. I allready have a new set of oem piston rings. By the way engine went down because piston skirt broke. (oem) any advise?

  2. #2

    Join Date
    Apr 2006
    panama city beach 'fl
    going thru that now myself,86 stock and going with all pro-x

    yamaha saying (and i 'll most likely screw this up) min .0039-.0049 I think ,hopefull you have mike's and bore gauge for setup

    and if #8 on cylinder with that dim. bore has wear BUT you can fit bigger piston think pro-x std-.001-.002-.003

    hope tihs helps

    later cd

  3. #3
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas

    cylinder size for Pro-X Piston

    Welcome to the forum hammerdog !

    for the cylinder #8 size you noted, in a Pro-X, it would be a B size.

    1~5 it uses "A" pistons
    6~10 it uses "B" pistons
    11~15 it uses "C" pistons
    16~18 it uses "D" pistons

    Yamaha cut these piston bores; piston (O.D.) for the GP1200R.

    79.899 ~ 79.902 (3.1456 ~ 3.1457)
    79.903 ~ 79.906 (3.1458 ~ 3.1459)
    79.907 ~ 79.910 (3.1459 ~ 3.1461)
    79.911 ~ 79.914 (3.1461 ~ 3.1462)

    There are 4 size pistons for the GP1200R from LaSleeve (pro-x). sizes A/B/C/D

    Standard Piston-to-cylinder clearance on any of these pistons should be:

    mm 0.100 ~ 0.105
    in 0.0039 ~ 0.0041

  4. #4

    1200r piston advice

    Was looking on prox website and could not find any prices. any one know how much there piston kits are?

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