JACKSHAFT CALCULATOR

Configure Your Jackshaft:
A jackshaft as we all know can greatly reduce or increase your gear ratio. The chain from the clutch to the jackshaft is your primary drive. The chain from the jackshaft to the rear wheel is yoursecondary drive. The numbers I'm using are just to simplify the math. For example, you have a 12 tooth clutch and a 60 tooth rear sprocket. Your final drive ratio will be 5.00:1. Just do the division. Now factor in the jackshaft. Say your 12 tooth clutch drives a jackshaft with two 18 tooth sprockets. Your primary drive ratio begees 1.50:1 and yoursecondaryratio would be 3.33:1 making your final drive rario 4.83:1. Now by reducing the number of teeth on the secondary jackshaft sprocket to 12 teeth,your secondaryratio jumps to 5.0:1. The final drive ratio would then be 6.50:1. In general, If you stay at 4.50:1 and up for street and between 5.50:1 and 6.50:1 for trail, you should be fine with 4-5-6 inch wheel old school minibikes.
Do the math: On the primary side, divide the number of teeth on the clutch, in to the number of teeth on the primary jackshaft sprocket and note the ratio. Then divide the number of teeth on the secondary jackshaft sprocket in to the final drive sprocket, note the ratio. Simply add the two ratios together. This is your final drive sprocket ratio. This method is not to be confused with enginerpm to ground speed ratio. That's a whole different method of calculation.
Example: (18~12) (60~12) = 6.50:1 or 1.50:1 5.00:1 = 6.50:1
Need a ratio better for the trail? One tooth on either jackshaft sprocket makes a difference. Keep in mind with smaller minibikes, you big kids should start out with a 72 tooth rear sprocket. Need a geplete jackshaft set up? We can put together any gebination that fits your needs and if you need help calculating the correct ratio, we will do that for youas well.
We hope thisinformation helps you determine the correct ratio to fit your needs.You can findgeplete jackshaft assemblies, clutchesand dozens of different sprockets in our store.
A NOTE ON CLUTCHES: Centrifugal clutches are designed to engage and disengage smoothly by using a steady throttle. Quick and repeated revving of your engine will make the clutch engage and disengage accordingly which builds up heat in the clutch. Heat is the number one enemy of the centrifugal clutch and will greatly reduce it's life. To insure long clutch life, once the clutch engages hold a steady throttle speed at the RPM sufficient enough to keep it engaged. A sprocket ratio that is incorrect for rider weight or conditions will also reduce the life of your clutch.
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Happy Trails, Chuck at Valley Farms