If you are looking for a way to introduce your children some of the basic principles of engineering, mechanics and construction, then building a go-kart out of a lawnmower engine can be a great project to start with. Making your own go-kart out of a lawnmower engine will keep the cost relatively low and will provide limitless fun and exposure to driving for your children.
Find an old push lawnmower that has a good working engine. You may even be able to find a broken lawnmower and repair the engine yourself to save more money and learn more about small engine mechanics. While checking out a lawnmower, make sure that it starts up and that the pull cord is not jammed, frayed or broken.
Disconnect the engine from the lawnmower body. To do this you will first need to disconnect the blade by using a wrench set. Use the socket wrench and sockets to unbolt the engine from the frame of the lawnmower. You can also cut any of the wires that are attaching the engine to the handlebar of the lawnmower. Disconnect the pull cord from the frame, but make sure that you do not break or tear the pull cord in the process.
Construct your go-kart if you do not already have a suitable frame for it. Make sure that the location for the engine is big enough and strong enough to support the weight of the engine itself. You can use a wooden frame or a combination of angle iron and metal tubing. When you design your go-kart, do not allow for it to have too much ground clearance, as that could cause the kart to flip due to a higher centre of gravity.
Using the same connection places where bolts previously anchored the lawnmower engine to the lawnmower frame, use steel brackets to connect the lawnmower engine to the body of your go kart. You will want to make sure that you are positioning the driveshaft cog so that it can be connected with the go-kart's axle cog. Reconnect any electrical connections and wires to the pedals so that you can control the throttle of the engine by a lever or pedal, depending on the design of your go kart. Depending on your design, you may also need to weld the brackets and engine to the frame of the go-kart.
Bolt the sprocket drive system together. The parts of the system include the double-flanged hub, wheels and tires, sprockets, brake drums, brake bands and a 3/4-inch-thick wall pipe for the axle itself. Use a washer and bolt system to put the brake drum and brake band on the axle, followed by the sprocket, flanged hub, and then the tire and wheel set. Make sure that you bolt the tire and wheel set on securely so that the vibration and rotation of the wheels do not unscrew the bolts to the tires.
Install a steering, brake, and throttle pedal kits so that your go kart is fully functional for driving. Unless you are an accomplished welder and machinist, you may want to opt for kits. You can also opt for a throttle switch, similar to that of a lawnmower, or you could even use the same throttle mechanism and connections from the lawnmower to operate the go-kart's engine speed.
Mount a seat in your go-kart with a seat belt for added safety and you will be ready to go.
If the lawnmower's axle cog does not fit or line up with the wheel's driveshaft cog, then you may need to buy a gear box that can transfer horizontal cogs to a vertical cog on the other end. Consider installing a roll bar for added protection for your go-kart's driver.