Anyone familiar with Grubee old Stage3 Gearbox

Discussion in '4-Stroke Engines' started by Irish John, Jul 21, 2010.

  1. Irish John

    Irish John Guest

    Hi Guys, All my bikes have Grubee Stage 2 gearboxes which are no longer available. I have recently got a Grubee stage 3 gearbox and I notice it has a different clutch (wider black thing) and also the final drive sprocket is a fixed 10T on a shaft that is smaller and so unable to take the 11T freewheel that I am used to.
    My question is this:
    Does anyone know what size of rear sprocket goes with this GB with its 10T fixed dive sprocket so that it performs to the same standard as the 48T on the old Mark2 GB?
    Can someone tell me why the operating cable is in 2 sections?
    Presumably this GB will makethe bike harder to pedal with the engine off because the gearbox final driveshaft will be turnng.
    I'd be very grateful to hear what people have to say about the Mark3 GB.
     
    Last edited by a moderator: Jul 21, 2010

  2. Irish John

    Irish John Guest

    In case anyone knows about the Mark 3 Grubee old style GB I wonder if anyone has experience of running the gears in an oil bath? If what was it like & did the GB get really hot and did the clutch slip?
     
  3. Irish John

    Irish John Guest

    Well this thread doesn't seem to have provided any answers. I'd have thought somebody would have known a bit about the Mark3 gearbox.
     
  4. My stage 3

    My first in frame build used the grubee stage 3. It came with a 11t free wheel which trashed out fast. I replaced the 11t with the 10 t and shaft from bicycle-engines.com The kit came with a 56T rear sprocket. I think the reason for 2 sections on the operating cable might be for cable adjustment however I took mine off and permanetly engaged the engager. pedaling my bike with the stage three with the 10t was not any harder because I used the HDaxle with the free wheel 56t sprocket. never used the rag joint sprocket stuff. Thing I did not like about the stage 3 was gear noise and the centrifical clutch grabbing and clanging really bad on take off. Had to get the bike rolling and then pull the recoil starter. Had the same symptons with the 4G which was fixed by replacing the junk bushing with a true oil lite. Maybe a true oil lite on the stage 3 would have cured its grab problem. As far as speed goes the stage 3 seemed to be a little faster than my 4G. Hope this helps you
     
  5. Irish John

    Irish John Guest

    Thanks Bill, that was very helpful. My Stage 3 came with a 10T rigid drive sprocket. I have never used a 56T rear sprocket because none of the Grubee gearboxes are built for them. Consequently I have a lot of surplus 56T sprockets. I'll make my own cable to fit the GB because I don't want that ridiculous joiner. The 10 T really needs to be replaced with an 11T shaft and that might be difficult given the zero parts availability.
    If I used the 10T I'd use a 44T rear sprocket because I read somewhere on MBc that one tooth up front equals 4 teeth at the back and given that the 11T ideally likes a 48T at the rear then the 10T would probably suit a 44T OK.
    I know the old Mark1,2&3 Grubee GBs are horribly noisy although I once had a very quiet one. It was the first one I ever bought - a Mark 2 from Bicycle-Engines.Com in Montana. I do hate the noise but I put up with it because the older models of GB work OK. Grubee cured the noise problem with the 4G but at what horrendous cost. It's like fixing tinea by amputating your foot.
    How could I get an Oilite bearing to fit the old style GB? I'd really like to know. How good are these bearings given that the bit that wears also involves the bell housing as well. It would be good to get an Oilite bearing a few microns larger so I could use the slightly worn bell housings instead of throwing them away.
     
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