Help with gear ratio with shift kit...

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KeithSeymour

KeithSeymour

Active Member
Sep 23, 2013
174
30
28
Northern Virginia
I have MotoMagz old roadmaster set up and the mount is the Sick Bike Parts mount with the jackshaft. He decided to keep the rest of the shift kit for his new build and I’m trying to figure things out. I have a Worksman Rear Drum wheel with a 23 tooth freewheel and I’m eventually upgrading to a 3 or 5 speed hub to shift but want to get the bike going for now. I’m not good with gear ratio so I was wondering if someone could tell me if this setup would work temporarily until I can save up money for the hub swap. I’m running a new 98cc lifan flathead btw.

11t clutch
17t Jackshaft in Sprocket
9t Jackshaft out Sprocket
30t chainring
48t chainring
back to a 23t single speed hub.

Here’s what MotoMagz ran:
11t- 44t (AKG jackshaft)
11t-17t (mount jackshaft)
36t chainring
44 chainring
23t rear wheel (5 speed internal hub)
 
S

Stormsorter

Member
Jun 10, 2010
122
1
16
Jasper County Illinois
You end up with a final of 2.47:1 . Not sure about your engine but for reference the 2stroke china likes something around 16:1 and you have to pedal up to 5-10mph before engaging the engine. And a 79cc HF Predator with centrifugal clutch can take off under the engines power around 13-14:1. Somewhere around here there's a link the the calculator I use called "gearratio.exe". The math is pretty simple too but I don't remember the equation due to heavy use of the calculator for speed.
 
KeithSeymour

KeithSeymour

Active Member
Sep 23, 2013
174
30
28
Northern Virginia
Wow, that's way too low for me. I'm trying to get 12.44:1. it's what I've heard is ideal for a four stroke setup. What sprockets would I need for that?

Keith
 
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