On the McCulloch two-cycle weed trimmers, the crankshaft spins the clutch, which in turn sends power to the trimmer head. The parts that make up the clutch are called the clutch assembly--and if any of the washers, springs or sockets go bad, the entire system can also fail, causing serious engine damage. Removing these assemblies requires two special tools: a piston stop and a clutch removal tool. McCulloch makes these tools, and it is a good idea to purchase them, as using other homemade tools can result in engine damage.
Disconnect the rubber spark plug wire. Remove the spark plug with the socket wrench. Insert the piston stop tool into the vacant spark plug hole.
Remove the four screws with the screwdriver, holding the engine to the shaft. Disconnect the ignition wires from the throttle and remove the engine from the shaft.
Unscrew the four screws holding the starter assembly housing cover in place over the pull cord, pulley and recoil spring. Remove the starter assembly from the engine.
Remove the four screws holding the clutch cover in place over the clutch assembly. Remove the clutch cover.
Turn the clutch by hand counterclockwise until the piston hits the piston stop tool. Place the clutch removal tool over the clutch hub. Turn the clutch's locking nut (in the centre) clockwise to remove the nut.
Slide off the clutch drum, rotor assembly and washer from the crankshaft.
Reassemble the clutch parts in reverse order: spring, shoes, rotor assembly, washer, clutch drum. Hold the clutch in place with the clutch removal tool while tightening the locking nut counterclockwise.
Set the clutch cover back in place. Tighten down the four screws. Set the starter assembly back in place over the clutch cover and tighten the four screws.
Reconnect the engine to the shaft by tightening the four screws. Hook up the ignition wires to the throttle. Remove the piston stop tool, reconnect the spark plug and spark plug wire.
If your McCulloch uses a spring clutch and clutch shoes, remove the shoes first, then the clutch spring. The spring is under a lot of tension so always wear eye protection.