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  1. #1
    SpeedJunky's Avatar
    Join Date
    Dec 2005

    Piston Questions

    Are the OEM pistons on the 05-07 GPR Cast or Forged?

    I am considering replacing the pistons, are you guy's going with OEM or Pro-x or Wiseco? Are these Forged or Cast?

    Any and all input would be helpful.


  2. #2
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    I do not know on the 05-07 but the earlier years are cast they are made by ART same as Pro-X. The Pro-X are a little beefier than oem and the ring lands are heavier. I prefer Pro-X to all others. I did not have a tremendous amount of luck with the forged Wisecos I ran in my older GP.

    Also Pro-X are coated
    Last edited by OsideBill; 01-20-2007 at 11:43 AM.

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

  4. #4
    Hydrotherapy's Avatar
    Join Date
    Sep 2006
    The Rock
    what sort of gains can you expect from pro-x over stock or is it just a heavy duty type of replacment that may be lighter or better made..will look for there web site for info but good fist hand knolage is better than sales talk

  5. #5
    Pro-x here as well.

  6. #6

    Join Date
    Jan 2006
    Taylor, MI 48180
    OEM's on the 05-07 are forged, wisecos are forged and the pro-x are cast. OEM 1200 are cast.

  7. #7
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas
    TCR is exactly correct
    And Reiterate with this info below

    What Is The Difference Between Pistons?

    Wiseco Performance Pistons

    * Forged piston. Complete kits include all pistons, rings, clips, wrist pins and top end gasket kit. Individual Piston Kits include one piston, rings, clips and wrist pin.

    Quality begins with a forging. Castings are porous and weak, Hypereutectic pistons are merely a cast piston with an increased silicon content. Although slightly better, they are not nearly as strong as forgings-which are pressed into shape with a 2000 ton press. Wiseco starts with certified extruded bar stock and forges our pistons in-house with the world's most advanced forging presses. Most aftermarket piston companies do not make their own forgings and therefore cannot achieve the level of quality control that Wiseco demands.

    ProX Performance Pistons

    * Cast piston. Designed to be a direct OEM replacement piston. Replacement rings fit both factory & ProX pistons. Can be used along with original factory piston meaning you can just replace one piston if you wish. Kit includes one piston, rings, clips and wrist pin.

    ProX pistons are precision machined on the latest, state of the art CNC equipment. The same low-expansion, low-friction piston alloy is used as is used for all major Japanese engine manufacturers. ProX Piston Kits are a first class solution to replace the original piston in your Personal Watercraft.

    WSM Performance Pistons

    * Cast piston. Original Series piston made to exact OEM specifications. Can be used along with original factory piston meaning you can just replace one piston if you wish. Complete kits include all pistons, rings, clips, wrist pins, gasket kit & top end bearings. Individual kits include one piston, rings, clips and wrist pin.

    Available in Original Series and Platinum Series kits. Original Series pistons are made to exact OEM specifications. Platinum Series pistons are made of high strength hardened aluminum designed to prevent skirt and ring groove breakage. Piston walls are treated with a nonabrasive coating which reduces heat and friction for extended life.
    Last edited by RX951; 01-20-2007 at 02:32 PM.

  8. #8
    Duke's Avatar
    Join Date
    Jul 2006
    New oem 1300 pistons are forged and have coating on skirts
    to reduce wear and friction.

  9. #9
    Join Date
    Nov 2005
    s fl
    Just to expand on this a little, the new oem forged pistons are not like the wisco forged pistons in one very important way.

    With the gpr new oem forged pistons, the cylinder wall to piston clearance is very similar to the cast piston specs. Very tight.

    The reasons for this are from the new alloys used in oem forged pistons. The expansion rate is similar to a cast piston.
    Imo much better that the older alloys used in forged pistons.
    Thank God for modern Technology!

    This is unlike the wisco's that uses a different alloy that requires a much larger cylinder to wall clearance.

    I personally like the tightest cyl to wall clearance possible, for longevity and power.

    The alloy wisco uses requires more clearance because of the excessive thermal expansion of the piston after warm up. Piston temperature determines piston size and cyl to wall clearance much more with older technology forged pistons than the new era of low thermal expansion alum alloys.

    Before fully warmed up wisco have blowby and excessive wear can take place if a proper warm up is not used for these pistons.

    Last edited by allcool; 01-20-2007 at 04:02 PM.

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