Rebuilding a go kart engine will include a complete breakdown, cleaning, inspection and replacement of all mechanical parts. As a result of this process, the engine will be restored to its original performance levels and will be ready for hours of wear and tear. Go kart engines are small and thus run in a high rpm range, requiring a rebuild for every 100 hours of use. If the engine is subjected to race conditions, it will need to be rebuilt every 20 to 25 hours to ensure it's performing at the highest level.
Remove the springs that attach the go kart's exhaust to the exhaust manifold and pull the pipe off. Place a clean rag in the exhaust port to prevent debris entering the engine's cavity.
Remove the air box and filter off the carburetor on the front of the engine by unscrewing the hose clamp with a screwdriver.
Unscrew the carburetor mount screws and pull the carburetor off the intake manifold. Wrap the carburetor in a clean rag and set it aside. Place another rag in the air intake manifold of the engine.
Jack the kart up on a stand, go to the underbelly of the kart and loosen the two engine motor mount bolts. Do not remove them entirely, but loosen them enough to allow the engine to slide back to its maximum rearward position.
Remove the drive chain from the primary sprocket. You may now unscrew the engine mount bolts and lift the engine off the motor mount, ensuring any wires from the ignition are disconnected at their junction points.
Unscrew the spark plug using a deep socket wrench.
Remove the head of the engine with an Allen wrench or socket set, allowing you to access the head gasket, piston head and valves. Use a socket set with an extension to remove the block from the motor's crank case. This will allow you to repair the cam, piston and transmission gears as necessary.
Loosen the piston bearing and rod assembly from the cam shaft with an extended T-handle Allen wrench. With the bearing removed, slide the piston and rod through the top of the head. Detach the cam shaft from the gear box by unbolting its single bolt from the main drive gear. At this point, you may also choose to unbolt and remove the transmission gears if they show excessive wear. The gears are held in place by a center nut that can be unscrewed with a socket wrench.
Slide the cam shaft out and inspect it for wear. If worn, replace it. If not, you may reinstall it in the engine later.
Use an engine spray cleaner and soft-bristle brush to clean the engine's interior chambers. Remove as much of the carbon deposits as possible. Once clean, dry the engine chambers with compressed air. It's important that you do not use water during this process.
Lubricate the interior of the engine chambers along with all parts in oil. Slide the cam shaft into place and secure it to the crank case with the center bolt. Reattach the crank case gears using their respective bolts. Next, slide the piston and rod assembly into place and reattach the bearing to the rod with the Allen bolts.
Use liquid gasket sealer to seal all metal-to-metal covers including the engine block, water pump/cooling jacket covers, crank case cover and head assembly. Bolt these covers on using a socket or allen wrench and a liquid thread lock on each bolt to prevent the bolts from backing out under vibration. With the engine complete reassembled, mount it to the motor mount block and ensure the engine is set as far back as possible on the motor mount to enable the drive chain to be attached.
Slip the drive chain over the primary sprocket and rear sprocket. Spin the rear axle and ensure the engine turns well. This will indicate that you've installed all parts correctly. Slide the engine forward to set the chain tension as per the manufacturer's recommendation. Reattach the carburetor and air box to the intake manifold using the mounting screws and hose clamps. Slide the exhaust pipe into the exhaust port and secure it by attaching the springs to the motor.
