Go kart forward reverse gearbox

[Mopar426hemi82]

I'm trying to run a forward/reverse gearbox on my off road buggy. It's powered by a 600cc katana engine. So the drive chains go like this. Engine to jack shaft, to gear box, then to each rear wheel. With a drive line between each wheel. I'm wondering what size gears I need on the jack shaft and gearbox? I have the stock gears that were on the bike, 13/53. Then from the jack shaft should I use a large gear or small gear to the gearbox. Cause the way it's set up I can't go bigger then a 17 tooth on the gear box. Should I go like a 13tooth from the jack shaft to the 17 tooth on the gear box? Or 30 tooth to 17 tooth?

 

[Rat]

I have the stock gears that were on the bike, 13/53. Then from the jack shaft should I use a large gear or small gear to the gearbox.

That comes out to a 4.07:1 final drive, HOWEVER your kart I'm sure is heavier than the curb weight of the whole functioning bike the engine came from so you're going to want to lower the ratio some to compensate.
I'd say 5:1 should be fine because of the motorcycle transmission and clutch... should be easy to get close with the gearbox as a secondary jackshaft in/output but going a little lower would be better than ending up high and smoking out the clutch pack.

Cause the way it's set up I can't go bigger then a 17 tooth on the gear box. Should I go like a 13tooth from the jack shaft to the 17 tooth on the gear box? Or 30 tooth to 17 tooth?

Big to little = High strain, Low torque, Higher top speed
Little to Big = Low strain, High torque, Lower top speed

 

[Scout]

That comes out to a 4.07:1 final drive, HOWEVER your kart I'm sure is heavier than the curb weight of the whole functioning bike the engine came from so you're going to want to lower the ratio some to compensate.
I'd say 5:1 should be fine because of the motorcycle transmission and clutch... should be easy to get close with the gearbox as a secondary jackshaft in/output but going a little lower would be better than ending up high and smoking out the clutch pack.

Big to little = High strain, Low torque, Higher top speed
Little to Big = Low strain, High torque, Lower top speed

Consider the size of the motorcycle rrear tire comprred to the size of the cart tire. The torque will be a bit easier on the small tire.

 

[Rat]

Consider the size of the motorcycle rrear tire comprred to the size of the cart tire. The torque will be a bit easier on the small tire.

600 katana shows 17" wheels... that means roughly 22" rolling diameter on the Bike.

So some 22x12-12 turf tires shouldn't be an issue at all