79cc transmission needed?

Luke Olsen

New Member
May 8, 2020
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I’m new to motorized bikes and I’m looking to put a predator 79cc on a trek 850, but I don’t want to spend the extra $100+ for a transmission/jackshaft. Can I pair a 44 tooth drive sprocket with an 11 tooth centrifugal clutch? Or is it best to have a transmission/jackshaft?
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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Besides reducing your gear ratio to one that your engine needs, a jackshaft also lines up the engine sprocket with the wheel's sprocket.

IFFF you could align your 10t engine sprocket with a 60t wheel sprocket, ya just might not need that jackshaft.
 

Tony01

Well-Known Member
Nov 28, 2012
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sf bay area
I’m new to motorized bikes and I’m looking to put a predator 79cc on a trek 850, but I don’t want to spend the extra $100+ for a transmission/jackshaft. Can I pair a 44 tooth drive sprocket with an 11 tooth centrifugal clutch? Or is it best to have a transmission/jackshaft?
Nope that’s a 4:1 which is way too tall even for a 212. But perfect for a go kart with small wheels which are also part of the gear ratio. Get the jackshaft. You want a 10:1. Too tall: smoke the clutch. Too low, blow the motor.