12 Series 4180 Powerhead
4.5 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 Cause Remedy
Engine does not start easily, stalls
at idle speed, but operates normally
at full throttle
Check compression Check combustion chamber for
excessive build-up of combustion
deposits,
check condition of valves and valve
clearances
Gasket on carburetor spacer flange
leaking
Install new gasket
Decompression lever sticking Install new cam gear
Muffler carbonized Clean muffler, or replace if
necessary
Crankcase damaged (cracks) Replace the crankcase
Engine does not deliver full power
or runs erratically
Secondary air seepage through
faulty gaskets on spacer flange
Install new gaskets
Piston rings worn or broken Install new piston rings
Muffler / spark arresting screen
carbonized
Clean muffler (inlet and exhaust
openings), replace spark arresting
screen (if fitted)
Air filter element dirty Fit new air filter element
Fuel/impulse hose severely kinked
or damaged
Fit new hoses or position them free
from kinks
Pump diaphragm torn Install new pump diaphragm
Decompression lever sticking Install new cam gear
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