grubee big bore kit?

Discussion in '2-Stroke Engines' started by jatgm1, May 20, 2016.

  1. jatgm1

    jatgm1 Member

    has anyone ever seen a big bore kit for the grubee model 2 stroke engines? something to bump it up to a larger displacement? they seem like common engines, seems simple enough to do but i couldnt find anything.
     

  2. 45u

    45u Active Member

    What motor and size do you have now? Keep in mind the Gurbee motors like one other use a longer rod. This is how you can tell by the piston.
     

    Attached Files:

  3. jaguar

    jaguar Well-Known Member

    not possible because of lack of metal between the stud holes and the cylinder bore.
    that is the 69cc

    the 48cc accepted 55cc and 60cc cylinders though. (I don't think they're available anymore)
     
    45u likes this.
  4. 45u

    45u Active Member

    All so check and see if you have 6mm or 8mm cylinder studs.
     
  5. jatgm1

    jatgm1 Member

    how do i check that
     
  6. jatgm1

    jatgm1 Member

    what about if you were to get longer rods and just make it larger vertically? is that done somewhere? or has any person on the forum ever done it by machining it themselves?
     
  7. 45u

    45u Active Member

    I need to know what size your engine is now! If it has 6mm cylinder studs then no way to do it as Jaguar said there is not enough spacing between the studs and the studs are too small. Yes a long rod can be put in if you have the equipment and the knowledge to rebuild a crank but you might be getting into more money then you can by a bigger motor.
     
  8. jatgm1

    jatgm1 Member

    its currently a 66cc, i was wondering if it could be done somewhat easily but i guess it would be much easier to just get a cruzzer motor and find a way to mount that.
     
  9. jaguar

    jaguar Well-Known Member

    a longer rod won't increase the piston stroke, only a different crank with a longer radius from crankshaft center to center of the crank pin that the conrod spins on.
     
  10. 45u

    45u Active Member

    If it is all ready a 66cc you all ready have a 47mm cylinder. So the only way you could get more is got to a 40mm stroke which will only give you a little over 69cc not really worth the cost to gain such a little bit unless the motor is messed up.

    Yes longer rods only slow down the piston speed and give a better rod angle.
     
  11. butre

    butre Well-Known Member

    Bert rod sells up to 52mm. be prepared to pay big money though. better option is to just use an engine that doesn't suck so much, like a 50cc KTM motor.

    50mm is the highest I'd go, at 52 you start getting wall flex real bad
     
  12. butre

    butre Well-Known Member

    someone sold one with a bigger stroke too, 46mm I think. don't remember who and I think they're out of business anyway
     
  13. jatgm1

    jatgm1 Member

    are their any posts on how to mount a ktm engine to a bicycle frame? or any sites that sell adapters of some sort? welding is not my strong suit, though i should learn.
     
  14. jatgm1

    jatgm1 Member

  15. 45u

    45u Active Member

Loading...