Questions about building a custom Go Kart


Old 10-17-07, 06:45 AM
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Question Questions about building a custom Go Kart

Before i begin asking questions i just want to let you know that i am no mechanic. I know very little about engines, drive chains, etc. I have been learning about them slowly but i have a couple questions about my engine.
I got it for free, along with a tractor that didn't work. Come to find out it was just the battery, unfortunately they moved away. Anyways, its a Briggs&Stratton Horizontal Shaft, 12.5 HP, IC Engine. Now i started this engine up before, and man i was so loud. I also have a John Deer tractor that has a 17 HP engine, and it is a lot quieter than that 12.5.

OK so my first question, is there a way to quiet the B&S Engine?

OK, i have a differential Axel that i got off the tractor that the engine was on. And i was wondering if i was to mount that on the Go Kart frame, does it matter how far it is away from the engine? I would have to run a belt from the engine to the Axel, would by minimizing the distance would i achieve more speed?

Last question, the drive sprocket, if it has more teeth what does that mean? More Torque?
If anyone can answer these questions that would be great.
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Old 10-17-07, 09:54 AM
Join Date: May 2006
Location: Iowa!!!!!
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I can give you some things to get you started. But we have some real cart guys on this forum who can get into the specifics of building and operating your cart, not only on a basic level but also on a performance level.

In terms of noise level, there are a variety of mufflers that can quiet your engine. Some of those will restrict exhaust flow more than others = lower performance. There are those that are a good compromise and I'm sure you'll be able to find one that works for you.

As far as placement of the engine relative to the driven components, that in itself, doesn't affect the gearing. However other considerations may apply. A longer belt may cause problems because of deflection. If you plan on clutching the belt to stop/start the cart you need room for that on the run of the belt. If you have a variable speed pulley on the engine, that wouldn't apply. Obviously on a cart you are limited on options, assuming the engine would be mounted behind the seat.

For your last question, your gearing would involve two components - the driving component and the driven. Relatively speaking if the two are the same size you will transfer at a 1 : 1 ratio. From that point the smaller the driving component gets the slower the speed and the higher the torque and faster the acceleration. The compromise on the latter is the top end speed attainable since you have "geared the unit down".

If you want to achieve higher top speed and are willing to compromise acceleration, you would use a larger driving component than that of your driven component.

An example of the last two would be 1 : 1 ratio - 16 tooth on the engine and 16 tooth on the axle. For more speed, less acceleration - 20 tooth on the engine and 12 tooth on the axle. For more acceleration and less top speed 12 tooth on the engine and 20 tooth on the axle. (These sprocket sizes are only for illustration purposes and may or may not be available).

Since you're using a belt drive you would be concerned with pulley size, but the same principle would apply.

Hope this helps,

Good luck with your project,

Old 10-18-07, 08:23 AM
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Ah yes that helped a bunch Bob, thanks!
Thank you very much!
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