Gear ratio help

[Darr245]

I am playing around in the garage and have a bad electric cart. I am converting to gas and have almost completed project. I have counted the rotation of the rear end. 6 rotations turn the rear wheels 1 full rotation. I would like to be in the 15 to 20 mph range. The engine is a 6.5 pred engine for now. What would be safe ratio to not burn up the clutch and to acheive the speed im looking for? I used 6.15 ratio with the predator engine on my mini bike build and it runs 34mph, there is a huge weight difference tho.

[cgtech]

What cart? What axle? If you really have 6:1 gears now, that's going to yield a top speed well over 30 mph. (maybe 40).

[Darr245]

From what i can tell its a dana rear end. The cart is a Melex 5 something. I marked wheel and spline shaft. It took 6 rotations on the spline shaft to turn rear wheels 1 full rotation. I beleave the gas engine is 3800 rpm. I just dont knoe which sprocket ratio to use.

[Darr245]

The cart is a Melex model 512, serial 913747. If anyone knows of a sprocket that will fit the rear splined shaft please let me know. I am going to run a #40 chain to a torqu converter.

[Darr245]

a few pics of the start of the build will post more as I wrap it up.

[classycarts]

Originally Posted by Darr245

I am playing around in the garage and have a bad electric cart. I am converting to gas and have almost completed project. I have counted the rotation of the rear end. 6 rotations turn the rear wheels 1 full rotation.

None posi rear end, one wheel in the air, rotate wheel 2 turns and count turns on input shaft. That will give you accurate gear ratio.

[Darr245]

The gas engine swap seems to be a success, currently using a stock 6.5hp engine, torque converter, and stock rear axle. Top speed was 21mph & well climb over curbs and pulls hard out of the whole. Going to drop rear sprocked 1 tooth and tune the engine to 8hp and see what it will do. Total build cost $425.00.