Lawnmower engines aren't just for lawnmowers anymore. If you have an old but still viable lawnmower engine, you may want to reconsider disposing of it. If you're handy with your hands and mechanically minded, you can undertake a myriad of projects that will save the engine from the landfill.
You can convert a lawnmower engine to a power generator. This generator is essentially a high-current DC-charging system. If you have a DC-to-AC power converter, it can be used as an AC generator as well. You will be able to use it to quietly extract power for lighting and cooking applications, and in conjunction with solar panels and wind generators as a backup system.
One of the most common projects for using a lawnmower engine is the go-kart. The challenge is that most lawnmower engines have a vertical driveshaft, but a horizontal driveshaft is needed to turn the axle of the go-kart. This can be accomplished using a V belt (commonly found in washing machines, cars and air compressors). Some basic tools are required, including a claw hammer, hand saw, chisel, hacksaw and electric drill.
Sci-fi fans imagined that by the 21st century we'd all be travelling about in hovercrafts. While that hasn't happened, it's still possible to build your own using a lawnmower engine for power. Using a 3 1/2-horsepower engine, you can build a hovercraft that will lift a 125-pound payload off the ground and move it at walking speed across flat surfaces.