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Old 03-13-2011, 02:55 PM
ocscully ocscully is offline
Motorized Bicycle Elite Member
Join Date: Jan 2008
Location: Orange County, CA
Posts: 373
Default Re: G4 and sickbikes shift kit

I've been riding a SBP 4-Stroke Shift Kit for over a year now, and during that time I've had it set up with the Grubee III Gearbox (3.7:1 reduction) and now the Grubee 4G for Honda Belt Drive (5:1 reduction). Both of these Drive units come with 11t freewheel output sprockets as standard equipment. There is a 10t fixed sprocket and shaft available for both drives as an option as well. When I ran the Type III Gearbox I used the stock set-up on the Jackshaft which is a 17t driven on the left side and a 9t driver on the right side. The Chainrings were a 48t driven and a 36t driver (30t chainring is the default/standard driver for the chainrings) to the rear cassette. When I switched to the 4G Unit, I changed the 9t driver on the right side of the jackshaft to an 11t driver and I changed the 48t driven chainring to a 44t. SBP recommends the the output of your reduction unit should be fixed (non-freewheeling). I made my 11t freewheels fixed sprockets by welding up the seam between the sprocket and the freewheel body, rather than switching to the 10t fixed sprockets from Grubee. Right now there seems to be no 4G drives available. The latest drives from Grubee are available in three different ratios? My guess is that bicycle-engines will probably be bringing in only one the 4:1 unit and maybe perhaps offer the other pulleys for purchase as parts?

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