Small Engines (Lawn Mowers, etc.): Briggs Stratton Modifications, briggs stratton, go cart

Question
I wanted to know if you could tell me the cheapest mods that gain the most HP for a Briggs 5HP and where I could buy them on the internet.

Answer
Have you checked the go-cart racing forums?  You can do anything from a header/air filter to offset flywheel keys, nitrous and even a supercharger.  Header, air filter and a flow-benched carb would provide the most bolt-on bang for your buck.

However, depending on what you plan on doing it may be cheaper to by a used race engine with carb, header and other goodies.

Eric