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Old 12-18-2008, 12:16 PM
ocscully ocscully is offline
Motorized Bicycle Elite Member
Join Date: Jan 2008
Location: Orange County, CA
Posts: 373
Default Re: From whom to get a 4 stroke?

The Grubee Kit offered by seems to be the best of what is currently available. It can be purchased with a motor, the HS clone of a Honda for around $400.00 +- or as an installation kit without motor for around $220.00+- and then you can get a Real Honda GXH50 from Small Engine Wharehouse for $210.00. Two other vendors are currently in the prototype/testing stage of building alternative reduction gearboxes/cvt? but are not currently available. Also the folks at Sick Bike Parts are working on building a version of their shifter kit to work with either the Honda motor or its clones.

The major difference between these 4-stroke kits and the HT 2-stroke is the need of the additional reduction gearbox. The HT 2-strokes have a built in reduction of 4.2:1 For the 4-stroke kits this primary reduction is provided buy a 3.7:1 reduction gearbox that is bolted onto the output side of the motor. This reduction gearbox seems to be the weak link in the 4-stroke kits. The current version of the Grubee gearbox (The Stage III) is supposed to be an improvement but has only just recently become available (Oct. 08) here in the US so its to early to tell how how much better it actually is. The early reports from the two new alternative prototypes from Quenten Gunther and Mike at Simpson MotorBikes have been good but I still have not seen any projected availability dates or pricing on either of them.

The Second major difference is the need for dramatically wider crankset for the 4-stroke kit. The currently available solution to this problem is a really bad one. It requires the use of a 9in. long BB spindle that uses a seperate cottered crank-sprocket and two seperate crank arms. This crankset also requires an adapter to mount it into the larger BMX/Cruiser BB shell which is an additional $30.00 - $40.00 depending upon which vendor you purchase the adapter from. Its a very ugly set up to say the least. There are whole threads on this crankset here and at the other forum.

The Third difference is the 4-stroke kits use centrifugal clutches and Pull starters rather than the manual clutch and pedal starting of the 2-stroke kits.


Last edited by ocscully; 12-18-2008 at 12:19 PM.
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