The centrifugal clutch, a very simple mechanism, uses an outside shell housing to encase shoes that expand when the engine reaches a certain RPM. Interior springs allow the clutch shoes to contract when the engine reaches a low idle state. Commonly used on minibikes, go karts, chain saws and other small engines, the centrifugal clutch transfers the main energy force from the engine to the driving wheel or drive sprocket. Installing a centrifugal clutch depends upon which type of engine and application you have, but the chore remains relatively easy for the do-it-yourself repair person.
Remove any fairing or plastic housing with a screwdriver or an appropriate socket, if you need to change the centrifugal clutch on a chainsaw or small ATV vehicle. Follow the chain from the rear driving sprocket up to the front part of the engine, to locate the clutch assembly, or refer to your owner's repair manual for the removal of the components needed to access the centrifugal clutch assembly.
Look for the tensioner adjustment on the chain or belt. On a chainsaw, the tension mechanism can be loosened with a Phillips screwdriver or a small socket. On a minibike or go kart, the bottom engine mounts must be loosed with a socket and wrench to move the engine on slots to pull the chain free. Once the tensioner or mounting bolts have been loosened, slip the chain off from the centrifugal clutch sprocket.
Spray WD-40 penetrating oil on the crankshaft where it joins with the centrifugal clutch. If you see a set screw in the clutch shaft, remove it with a small end wrench. Use a socket and wrench to loosen the main nut and thrust washer from the end of the crankshaft and pull the clutch straight out from the shaft on its key way.
Do not lose the key unless you intend to replace it with a new one. If the clutch appears stuck, use a gear puller to break it free, by slipping the curved tines of the gear puller over the back of the clutch housing and turning the main gear puller bolt clockwise until it slides off the shaft.
Clean the crankshaft off with WD-40 and a rag. Place a new key on the crankshaft key way. Align the new centrifugal clutch over the key way and push it forward onto the crankshaft until you feel resistance. Grease the end of the crankshaft threads with anti-seize compound. Place the thrust washer and nut back onto the crankshaft and only partially tighten down the nut with the correct size socket. Refer to your owner's repair manual for the proper torque number. Tighten the nut down with a torque wrench to the proper specification.
Replace and tighten the set screw with an end wrench, if you have removed one. Position the engine so you can align the chain (or belt) with the clutch sprocket. Make it straight. Pull the engine back against the chain so you have about 1/4-inch free play in the chain. Tighten the engine mounting bolts. For the chainsaw, adjust the tensioner bolt or screw with a socket or screwdriver until you have the correct tension on the chain. If in doubt about the free play, refer to your owner's repair manual.
Place the housing back onto the engine with a socket or screwdriver, if you had to remove one. Start the engine and look for proper clutch align and chain tension.
