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Old 08-13-2014, 11:18 AM
cschade cschade is offline
Motorized Bicycle Senior Member
Join Date: Aug 2014
Location: United States
Posts: 50
Default Re: Gear ratios for HF bike -- please help!

Originally Posted by FFV8 View Post
Experience tells me that with no pedals you will need a 14:1 overall ratio with a 79cc engine.

Pedals are not needed here in NV either. Without pedals, it must launch on the clutch. I have seen various ratios tried within our group, and one guy has to flintstone launch the bike at every stoplight - I think he is at 10:1

Using a Hilliard Extreme Duty clutch with the 3000 rpm springs installed helps a lot. You can at least get the engine up on it's torque peak at launch.

Here are some pics of the bikes with various jackshaft arrangements:

All of those 79's are running a PZ19 style carb of one kind or another, and they will all hit 6200 rpm

So to hit a 14:1 ratio, what size sprockets do i need for clutch, jackshaft in, and jackshaft out, assuming a 28 tooth rear sprocket?
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