10 MS 311, MS 391
3.3 Chain Lubrication
In the event of trouble with the 
chain lubrication system, check and 
rectify other sources of faults 
before disassembling the oil pump.
.
Condition Cause Remedy
Chain receives no oil Oil tank empty Fill up with oil and check setting of 
oil pump if necessary
Oil inlet hole in guide bar is blocked Clean oil inlet hole
Intake hose or pickup body clogged 
or intake hose ruptured
Fit new intake hose and pickup 
body
Valve in oil tank blocked Clean or replace valve
Teeth on worm worn Install new worm
Worm drive spring broken Install new worm
Oil pump damaged or worn Install new oil pump
Machine losing chain oil Oil pump body damaged Install new oil pump
Oil pump damaged or worn Install new oil pump
Oil intake hose connection 
damaged
Install new oil intake hose
Oil pump delivers insufficient oil Oil pump worn Install new oil pump
Worm drive spring not engaged in 
clutch drum
Engage drive spring in notch in 
clutch drum
Oil pump delivery rate set too low Adjust oil pump
(only on version with adjustable oil 
pump)