Is there a way to add a 2 or 3 speed transmission?

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cobrafreak

New Member
Feb 16, 2011
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sacramento ca
I have a Grubee Skyhawk 2 stroke 66cc and I would like to add a gearbox somehow that still retains my rear hub intact. I wanted something that goes between the engine and the rear sprocket. Is anything like this made? Thanks.
 

cobrafreak

New Member
Feb 16, 2011
1,049
9
0
sacramento ca
I was thinking along the lines of something like this: Get a Sturmey/Archer 3 speed hub and put a 415 sprocket on both ends so it's the same size as the sprocket off the engine. So you have a rear sprocket with a chain sprocket on both ends. Then you have another hub, but it is just a front hub, and it is set up the same way, with a 415 sprocket on both ends. You have both hubs sandwiched in between two small plates, so they both rotate. Then you mount the plates to your seat tube. All you need to do is run the engine chain onto the hub that is the "front" hub, the hub that does not shift. We will call this the left side of the bike. On the right side of the bike you are going to have a very short 415 chain to connect both of these hubs, then finally the last chain wheel on the left side of the bike will go to the rear sprocket. You would be able to shift at any time you wanted to and still retain the hand clutch. It wouldn't be very wide. I'll add a diagram. I think it would be doable. The nice thing about this set up is could be retrofitted onto almost any bike

 
Last edited:

2door

Moderator
Staff member
Sep 15, 2008
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Littleton, Colorado
As long as you get the gearing right I don't see a reason it shouldn't work. I have a three wheeler that had the same concept from the factory. It was originally pedal powered but it had a Sturmey 3 speed hub mounted mid way between the pedal crank and the rear axle. Very much like your idea. The challenge, or the unknown here is if the Sturmey hub could take the abuse of the motor used like your idea would require. Good luck, let us know if you try this.
Tom