How to Lubricate a Clutch Drum Bearing

Maintain peak performance by performing routine maintenance on your chainsaw.

Centrifugal clutch systems within chainsaws have clutch drum bearings. The bearing is actually a small needle between the hub of the clutch and the crankshaft. Operation of the saw causes significant heat and friction. Oil that drips off the sprocket provides minimal lubrication. However, the bearing requires more lubrication to function properly. When the bearing isn't lubricated properly, the crankshaft grinds against the drum, shoes and plate inside the clutch assembly. The entire crank typically requires replacement when damage occurs to this extent, and full crank replacements can be expensive.

Things You'll Need

• Assorted wrenches and sockets
• Screwdriver set
• Piston stop tool
• Shop rag
• Engine grease
• E-clip

Instructions

1. Twist the nuts on the clutch cover counterclockwise to loosen them. Position a screwdriver tip inside the hole that sits between the nuts on the bar.

2. Rotate the bar tensioner screw counterclockwise to add slack to the chain. You can see the slack collect under the guide bar. Remove the bar nuts and the clutch cover.

3. Pull the chain and guide bar off the drive sprocket. Pry the rubber cap off the spark plug and remove the spark plug from the engine block.

4. Insert your piston stop tool into the spark plug input. Rotate the clutch drum manually until the piston stop tool is against the piston.

5. Pry the E-clip off the crankshaft and remove the sprocket, clutch drum and needle.

6. Clean off the sprocket, clutch drum and needle with a shop rag. If the components are not damaged and they are all in working condition, proceed with the lubrication process. If you find damage or malfunction upon inspection, replace any damaged components before proceeding to the next step.

7. Coat the entire surface area of the needle bearing with engine grease.

8. Replace the needle, sprocket and drum in the crankshaft. Install a new E-clip onto the upper section of the drum. Return the bar and chain to their respective positions. Bolt the clutch cover back on and screw the bar tensioner screw down tightly.

Tips & Warnings

• Do not attempt lubricating the clutch drum bearing while the chainsaw is turned on.

References

• Madsen's Shop and Supply Inc.: Clutch Maintenance on Pro Saws
• "Stihl 021, 023, 025 Instruction Manual -- Owner's Manual"; Andrew Stihl; 2001