Help with ordering piston, grube gt5

Discussion in '2-Stroke Engines' started by rogergendron, Sep 4, 2013.

  1. rogergendron

    rogergendron New Member

    Hey guys I am new to the forum but a very experianced mechanic.

    I have a problem here. It seems like there are at least 3 dif piston types for the same style engine.

    I am doing a rebuild ... Port polish port matching exe .... And I am litteraly done, all I need to do now is order a new piston rings and clips. Then trim the skirt to match my intake port and grind a relief in the piston for the exahst and side ports.

    But I do not know the part # of the piston I need

    I jave the grubee gt5 my piston has only an arrow on top and when the piston is on a flat surface the top of the wrist pin hole measures 1 1/8 up from the surface . The closest piston I found said it was a type b and the hole measured 1 1/16 up ? Thats a 1/6 off and will alter port timimg ! The other said 15/16 up. Type a I think there are more but they are marked differant than mine on top . I want the correct dome and port timing here so I need to be shure I am getting the roght piston .

    Can you guys help .

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Get it from
    They sell Grubee SkyHawk GT 5 motors and parts.

    Rob and Gregg answer the phone and will treat you right.

    They also sponsor the races and race.
  3. Purple Haze

    Purple Haze Active Member

    The main difference is the compression height. (distance fron pin centerline to piston top) The Super Rat had a 40mm stroke, while most all others have a 38mm stroke. Not a big problem if you know how to shim the cylinder to get "0" deck height. Also, there is a piston with a domed top which I don't recommend, as it impedes flame travel, stick with a flat-top piston. It's also a little lighter, which helps balance and quicker revs. By the way, I don't think they make the Super Rat anymore, but still sell parts for them. Hope this info helps.
  4. jaguar

    jaguar Well-Known Member

    If you're worried about port timing you have to measure to piston top edge, not the center top of the piston.
  5. KCvale

    KCvale Motorized Bicycle Vendor