Page 1 - Overview of Building
Page 2 - Materials for Go Karts
Page 3 - Go Kart Frame
Page 4 - Go Kart Seat
Page 5 - Go Kart Steering Overview
Page 6 - Go Kart Spindles, Axles
Page 7 - Go Kart Engines, Exhaust
Page 8 - Go Kart Throttle, Brakes
Page 9 - Go Kart Clutch, Sprocket
Page 10 - Go Kart Parts Sources
Page 11 - Our New Site
Go Kart Engines:
Most often used is a 5-8 HP motor commonly used in tillers. They should be horizontal shaft.
Motors pulled from lawn mowers are usually vertical shafts, and won't work when flipped to a horizontal position without obscene customization. To accomplish using a vertical lawn mower engine in a go kart, you'd need to reroute the gas, carb, oil slinger... Well, it would get complicated -- they aren't made to do it.
Lawn mower rear ends could be used to transfer the power from vertical to horizontal, but the lawn mower guys we've spoken to say that they aren't strong enough to handle the abuse a go kart would see. We're told that they have too many aluminum parts.
In short, stick with the horizontal engines.
Check prices on engines at Northern Tool.
Go Kart Custom Exhaust
The function of the exhaust system is to get the outgoing gases away from the motor as quickly as possible. The more efficiently the exhaust exits, the better the motor will perform. A muffler serves to quiet the exhaust gases, yet doing this constricts the outgoing gases. Even so, most people prefer some amount of a muffler since open pipes (though the most efficient) are also really loud.
If your motor has a constrictive exhaust, then one customization you can easily accomplish is to make a custom exhaust that muffles the engine as much as you need, and also eliminates unneccessary turns and constrictions in the system. Each turn in the exhaust means more constriction, and less power.
Most small engines are threaded at the exhaust port. Check the theading, it should be a common pipe thread, meaning that welding a custom header is possible. Remember that you want high-flow, and bends and restrictions lessen the flow.
Check for other styles of lawn mower mufflers that also use this thread pattern. You can remove some of the constrictions and make the muffler higher-flow. The pic is of a standard Briggs and Stratton exhaust.