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Old 08-22-2009, 12:52 PM
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tyrslider tyrslider is offline
Motorized Bicycle Elite Member
Join Date: Sep 2008
Location: RainCity
Posts: 958
Default Re: Pedal start for four strokes

Gearing to the pedal crank on my 4 stroke shifter is about 31.2:1 (I need to reduce mine a little more 35:1 ish). Unlike a single speed bike that is reduced 16:1 ish, your pedal crank to rearwheel is geared up i.e. multiplied (typical cruiser 1 speed is 48/18 or 1:2.666, 1 crank rotation = 2.666 wheel rotations). So on a jackshaft set up you need to reduce engine speed much more 'cause at the pcrank you gear it back up again.

You would need a 315 tooth chainring for a 9 tooth op sprocket.

Good thinking though! And I still love the pedal start Idea though the only benefit I see is a slightly narrower motor.
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