Stihl chain saws operate with a centrifugal clutch system that includes a clutch drum, sprocket, needle bearing, clutch shoes, clutch plate and a spring. These systems frequently run at speeds of over 10,000rpm's causing a lot of heat and friction inside the engine. If the clutch isn't lubricated properly the crankshaft can grind on the clutch shoes, the clutch plate and the clutch drum, which can cause your clutch to blowout. When you lubricate the clutch, you are really lubricating the needle sprocket, which sits on the crankshaft and the inner ring of the clutch assembly.
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Things you need
- Socket wrench
- Piston stop tool
- Engine grease
Loosen the clutch cover's nuts with the wrench. Turn them counterclockwise until they are about finger tight. Insert the screwdriver into the hole in between the two bar nuts. Loosen the bar tensioner screw by turning it counterclockwise until you notice the chain falling slack beneath the guide bar.
Remove the bar nuts all the way with your fingers. Pull off the bar nuts and the clutch cover. Lift the chain and guide bar off the drive sprocket. Set these parts aside in another area.
Lift the spark plug's black rubber boot from the tip of the spark plug. Use the tip of the screwdriver to gently pop the boot off if it's stuck. Place the socket wrench into the spark plug hole. Loosen the spark plug with the socket wrench and take it out of the engine.
Stick the piston stop tool directly into the open spark plug hole. Twist the clutch drum by hand until you notice the piston stop tool contacts the piston.
Wedge the E-clip off the crankshaft by popping it off with the flat tip of the screwdriver. Throw the clip away because it cannot be reused. Pull the sprocket, clutch drum and needle bearing from the crankshaft.
Wipe these parts clean with a rag and inspect them for signs of visible damage. Replace any damaged parts. Shake the needle bearing lightly by your ear. If you can't hear a light shaking sound from the bearings, they have frozen up and you will need to replace the needle bearing.
Squeeze out about a fingertip's worth of engine grease from the tube of grease. Wipe the grease along all of the individual bearings on the inside and outside of the needle bearing.
Install the needle bearing, sprocket and clutch drum back onto the crankshaft. Install the replacement E-clip onto the top of the clutch drum. Set the bar, chain and clutch cover in place over the clutch assembly. Tighten the clutch cover's bolts with the wrench and tighten the bar tensioner screw with the screwdriver.
Tips and warnings
- Follow the lubrication recommendations in your owner's manual.
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