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Jack Shaft Kit
Change the Gear Ratio of Mini Bikes and Go Karts
A jack shaft will increase or decrease your gear ratio depending on the arrangement of the gears. Most often, it increases it for more power, less speed.
The shaft has 3/16in. keyway. Comes with 10 and a 14-tooth sprockets which take #40 size drive chain.
Mounting hardware: two standard 3/4in. I.D. bearings with hangers and a 3/4in. I.D. collar. Two keys, 3/16in. x 3/16in. x 3/4in.
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A jack shaft is often necessary when the engine is too far from the drive wheel. You don't want your run of chain to be too long, and the jack shaft effectively makes it have two short runs of chain.
You could alternatively use an idler sprocket that would keep tension on the chain. But the jackshaft is a very good choice.
The other use of the jack shaft is to change the gearing. A 1:6 gearing will generally go arounn 30 MPH. When increases, the low end power will increase and the top end speed will decrease. So if you use the jackshaft to increase the ratio, you may wish to use a smaller sprocket on the drive wheel to compensate for lost speed, if speed is your goal. Alternatively you might want an even larger than normal sprocket if rock climbing is you goal.