Sprocket choice for my mini car

[KmanShowfam]

Hello all, I am in the process of building a Kart and trying to decide was sprocket combination will give me decent torque and good top speed. The wheels and tires are 11” tall. In browsing this site, I have found that typical setup is 12 front and 72 rear. If I’m calculating correctly, that will get me 17.8 mph at 3600 rpm. I would like a little more top speed. Does anyone have any suggestions??

Another question, the mini car is a ‘78 and came with a 3hp Briggs. Are the dimensions of a 5hp from mid ‘70s into ‘80’s the same? The base of the motor to mount? You know, no Substitute for cubes!!

Thanks for your time!!
Kevin

 

[Rat]

Hello all, I am in the process of building a Kart and trying to decide was sprocket combination will give me decent torque and good top speed. The wheels and tires are 11” tall. In browsing this site, I have found that typical setup is 12 front and 72 rear. If I’m calculating correctly, that will get me 17.8 mph at 3600 rpm. I would like a little more top speed. Does anyone have any suggestions??

Another question, the mini car is a ‘78 and came with a 3hp Briggs. Are the dimensions of a 5hp from mid ‘70s into ‘80’s the same? The base of the motor to mount? You know, no Substitute for cubes!!

All 5hp briggs base dimensions are the same, and iirc are common to the 6hp as well

IF you update to a modern engine, it wont matter if its an OHC or OHV, the bolting will then need to be updated.
A Honda GX series (OHC) is more compact than an OHV, in the sense it is stacked vertically like a flathead instead of having a 35° or whatever it is cylinder angle from the base like ALL OHV engines have.

The only way you'll get more speed is to update everything, bigger engine, slightly bigger tires, different gearing, and a TC for good measure because Hilliard clutches suck when not on a race track doing constant full throttle

 

[KmanShowfam]

So a 12t front and 72t rear sprocket is a good ratio? I want to keep it somewhat original, with the Old Briggs motor, painted Chevy orange of course!

 

[Denny]

You will need to keep that ratio to keep from burning up clutches on take off.