go-cart: engine id + sprocket selection

I've been offered, but don't yet have, an old Briggs and Stratton 8HP snow blower engine. For the time being, no model and type number can be found on the engine. Rust has probably covered the numbers. I've got pictures I can email out to anyone who's a B&S model-identifying expert.

I imagine the 8HP will be plenty HP to power a go-cart with light off roading capabilities. How do I choose the sprocket size for this engine ?

I'd like my young children to ride it. I've seen speed reducing mechanisms for go-carts engines. Can I just limit the throttle's range of movement instead ?

Thanks!

PS My I-want-for-Christmas list now has plenty of choices (a disk brake, centifugal clutch, B&S small engine repair manual, off roading tires, axles, a welder, welding classes, steel tubing, extra life insurance, time, gas, etc.) Guess I'll be spending more time on ebay !

 

I would start with a high reduction (small sprocket on engine, large sprocket on axel). That will give you good acceleration and torque for off-road while limiting the top speed. The speed and hill climbing ability of the cart will also depend on the size of your back tires. Bigger tires will make the cart go faster while hurting acceleration and torque.

Just guessing but I'd start with about 13 teeth on the engine and 70 teeth on the axel.

 

Thanks Pilot Dane for the sprocket and tire advice. I'm not sure what to expect for speed, but I do prefer the extra acceleration and torque. You suggest smaller tires. I had instinctively thought of large tires for additional traction (although I not planning on a mud slinger/skipper) and ground clearance. Will smaller tires work well off road? What sizes do you recommend ?

 

Bigger tires are probably better for off road. The larger diameter helps smooth out the bumps and provides more ground clearance. A large tire on a small rim (lots of sidewall area) will do a lot to smooth out the bumps. Don't go monster truck with your tires. Larger tires have more mass and take more power to get turning, and they can put more of a load on your axels and stearing hardware. You will just need to go with a bit more reduction on your sprockets to offset the larger tires.

You can look at golf cart web sites. They sell lots of 20-22" high tires about 8-10" wide mounted on 10" rims. A hundred dollars could probably get you a pair of new tires & rims. You can also see what Wally-World has.

 

Wow I wan't thinking that large. I was thinking more along the lines of a knobby pattern 145/70 - 6 tire. Am I thinking too small ? Should I get 4 of the same size or should I use smaller tires up front ?
Pilot Dane: Thanks a million for all your advice

 

Use whatever tires you like. You are doing some real customizing so make it the way you want, that's half the fun of building something yourself.

 

Hey Pilot Dane, I hope I didn't offend you with my previous message. That was really not my intention. I was hoping for more idea exchanges.

I thought the like of a 145/70 -6 tire was large (when compared to go-cart racing tires). However, I've never built nor drove something like this. If I'll end up spinning and getting stuck all the time on trails (on top of wasting time and money) with the tire size I had in mind, I'd be grateful it you would tell me so.

Being from Quebec, I know what to expect from a 8HP snow blower's ability to propel snow, but I don't know how this power can translate to moving a cart. Given my old engine and the fact that I'll be using the high reduction setup you suggested, should I think bigger tires? What kind of speed can be obtained with the different tire sizes (I'm a light weight)?

 

I am certainly not offended. I just think that you are building something with your two hands (darn close to art in my mind) so you should do what YOU want. I like it when people build something different just because they like the way it looks or it feels right.

My racing kart has tires about 11 inches high and very wide. They are great for acceleration and traction when turning, but would look really funny off the race track.

The tires on my golf cart are about 18" high x 8" wide. They work great in the mud and snow. The large tire puts a very light pressure on the ground.

The 145/70-6 tires you are talking about are quite common on go carts so you can sure that they will work. Their smaller size will certainly give you better torque for hill climbing, but they may leave you stuck if you get some snow. They are very inexpensive and wheels, hubs & axels to fit them are commonly available.