Engine - Stihl MS 261 User Manual

3.7

Engine

Always check and, if necessary,
repair the following parts before
looking for faults on the engine:
- Air filter
- Fuel system
- Carburetor
- Ignition system
Condition
Engine does not start easily, stalls
at idle speed, but operates normally
at full throttle
Engine does not deliver full power
or runs erratically
Engine overheating
18
Cause
Oil seals in crankcase damaged
Crankcase leaking or
damaged (cracks)
Piston rings worn or broken
Muffler / spark arresting screen
carbonized
Air filter dirty
Fuel hose kinked or torn
Decompression valve is not closed
Insufficient cylinder cooling. Air
inlets in fan housing blocked or
cooling fins on cylinder very dirty
Air flow path into fan housing dirty
Remedy
Replace the oil seals
Seal or replace the crankcase
Fit new piston rings
Clean the muffler (inlet and
exhaust), replace spark arresting
screen, replace muffler if necessary
Clean or replace air filter
Fit new hose or position it free from
kinks
Close, check and replace
decompression valve if necessary
Thoroughly clean all cooling air
openings and the cylinder fins
Clean air flow path into fan housing
MS 261, MS 261 C