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Old 03-10-2011, 01:44 PM
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primusbike primusbike is offline
Motorized Bicycle Newbie
Join Date: Mar 2011
Location: nys
Posts: 16
Default Re: Building 4stoke shift kit

Originally Posted by ocscully View Post
I too have the SBP 4-stroke Shift kit with the Honda GXH50 motor. I started out with the Grubee III Gearbox which provides 3.7:1 reduction and used the SBP 48t and 36t chain rings. I rode this set up for 7months and 6000+ miles. Back in October I switched to the Grubee 4G for Honda Drive which is the 5:1 reduction. With the extra reduction provided by the 4G unit I substituted a 44t chainring for the 48t to bring everything back to balance. Being able to fine tune the ratios relatively inexpensively is one of the beauties of SBP Kit. They have a variety of chainrings available and all are around $10.00 or less. Currently it seems that all vendors are Out of Stock on the Grubee 4G drives and Kits. You may find that when the come back in stock this Spring that they may not offer the 5:1 Reduction. Alot of folks seem to think that 5:1 is to much primary reduction. The Newer 4G drives seem to be most commonly found using the 80t pulley offering 4:1 reduction. Either one of these reduction can be easily adapted to the SBP Shift Kit.

Wow. That is exactly what I needed to know. Thank you. I would prefer a belt for initial reduction just because high speed belts are quieter than gears. Has anyone mounted a belt cog to the output shaft of a 4G? In other words, instead of a chain to transfer power from the 4G to the jackshaft, another belt? Im not sure how the sprocket is fastened to the end of the jackshaft, but surly a similar cog belt pulley could take its place...
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