An oil pump on a Stihl chainsaw regulates the amount of oil pumped into the bar to lubricate it during operation. Proper chain lubrication is essential to ensure maximum performance of your Stihl. Damage to the oil pump will cause poor lubrication, which can cause excessive heat and friction on the bar and engine. Replacing the oil pump on a Stihl saw can be difficult and replacing one without proper saw knowledge can result in serious engine damage.
Turn off the saw and release the chain brake. Take off the clutch cover, bar and chain. Put them aside in a safe place.
Drain all of the oil from the oil tank. Remove the spark plug and insert the saw's starter cord into the hole to block the piston from moving.
Unscrew the oil plate located in between the metal guideposts near where the bar attaches to the engine. Remove the chain brake handle screws and take off the chain brake.
Use the screwdriver to pop off the E-clip holding the flywheel in place over the clutch. Take off the washer and sprocket. Replace those parts if broken or heavily worn.
Pull off the clutch drum and, with the clutch removal tool, release the clutch's centre bolt. Stihl clutches are left-hand loosening, so twist the screw clockwise to unscrew.
Unscrew the bolt with your hand and remove the entire clutch off the crankshaft. Underneath you will see the pump assembly.
Unscrew the oil pump's mounting screws. Pull the entire oil pump out of the engine.
Disassemble the pump and disconnect the plunger from the engine.
Install oil pump kit following the manufacturer's guidelines. Lubricate the worm drive, spring drive and plug in the new oil pump.
Put the saw back together following these directions in reverse order.
You may need to use a small hammer or mallet to tap on the clutch to get the bolt to release.
If in doubt about removing the oil pump, take the saw to a licensed Stihl mechanic. Improper oil pump installation can cause serious engine damage.