Lubrication for the bar and chain on Stihl chainsaws comes from an oil pump, which is attached to the oil tank. The pump is attached to the worm drive on the clutch, so when the clutch is spinning the pump is also engaged. Oil is distributed to the bar by a hose and a small nipple, which your guide bar is seated on. This nipple is attached to a small hole on the rear of your bar and oil is spread across the chain from here.
Testing the Oil System
Start the chainsaw and run the chain for a while. Throttle the saw and hold the tip close to a piece of cardboard or freshly cut wood. Look for a light splattering of oil. If there's oil, nothing is wrong with your system.
If the oiler is not working, shut the saw off. Loosen the bar tensioner screw between the bar posts. Unscrew the bar nuts with the wrench. Remove the bar cover, bar and chain.
Check the bar's oiling hole to make sure it's not clogged or dirty. Clean it with the knife. Spin the bar's nose sprocket with your hand if your bar uses one. If it doesn't spin freely, lubricate with engine lubrication. Insert the lubrication gun into the oiling hole on the tip and pump one to two times.
Unscrew the oiler plate that sits next to the bar posts and covers the oil pump. Take the edge of the oiler plate, insert it into the top end of the guide bar's slots. Drag the plate down the length of the guide bar, cleaning both slots of compacted sawdust.
Drain the tank of any old oil. Scrub it with the brush and rag to clean it. Pull out the pickup body inside the tank with the needle nosed pliers. Disconnect from the engine and replace the pickup body, suction and hose.
Start the saw with the bar cover, bar and chain off. Depress the throttle and look at the oiler's nipple. If the pump is working properly, you will see a light dribble of oil come out. If it's not working properly you will need to service your pump and replace the hose.
Removing the Oil Pump
Pull off the spark plug's rubber boot. Unscrew the spark plug with the socket wrench. Remove the spark plug and insert the piston stop tool into the hole. Remove the starter cover and turn the flywheel by hand until the piston contacts the stop tool.
Unscrew the brake band's cover screws with the star Allen wrench. Remove the brake spring from its anchor pin with the end of the screwdriver. Caution: this spring is under a lot of pressure and may pop out unexpectedly. Remove the brake band from its seat on the crankshaft.
Remove the E-clip that holds the washer, sprocket and clutch drum to the crankcase. Pull them off the crankshaft. Unscrew the clutch's bolt with the socket wrench. Loosen the bolt clockwise and remove from the crankshaft. Pull off the washer. Remove the clutch shoes and the clutch spring.
Twist the worm and drive spring clockwise and remove them from the crankshaft. Unscrew the oil pump's mounting screws. Take the oil pump off its seat and remove from the crankshaft. Remove the bottom washer.
Disassemble the oil pump. Knock out the spring pin on the bottom with a punch. Pull the bottom control bolt from its hole and remove the O-rings. Pull the end plug off housing and remove the pump piston, spring and washer.
Repairing the Oil System
Wash all the disassembled parts in a strong cleaning solution, like carburetor or engine cleaner. Scrub clean with the brush if necessary. Inspect all parts for damage or heavy wear. Replace as necessary.
Reassemble the oil pump in reverse order. Use new O-rings and lubricate the pump piston and worm gear with engine grease.
Remove pump delivery hose from the engine. Pull it out with the needle nosed pliers and replace the line. Use the metal wire to insert the new hose into the mounting flange hole.
Reconnect the oil pump to the engine. Reinstall the rest of parts in reverse order. If oiling problem persists, replace oil pump.