Yamaha EF3000iSE Service Manual page 190

ENGINE SPEED IS UNEVEN
Check fuel level.
SUFFICIENT INSUFFICIENT
Check if fuel is deteriorated.
GOOD NO GOOD
Check if fuel cock, fuel pipe, fuel
hose and fuel pipe strainer are
clogged.
GOOD NO GOOD
Check spark plug for dirt and
check spark plug gap.
GOOD NO GOOD
Measure valve clearance.
OUT OF SPECI-
GOOD
FICATION
While the engine is operating, pull
the choke knob approximately 1/3
to 1/2 way out, and then check the
engine operating condition.
STABLE UNSTABLE
Check for air suction due to a
damaged throttle shaft seal, car-
buretor joint, or gasket.
GOOD NO GOOD
Check if slow or main passages
such as, the pilot jet and main jet,
in the carburetor are clogged.
GOOD NO GOOD
**
Check valve face and valve seat
for wear.
GOOD WEAR
Check if there is seizure or wear
on the piston, piston ring, or cylin-
der.
SEIZURE OR
GOOD
WEAR
Check the condition of the throttle
control system. Refer to "THROT-
TLE CONTROL SYSTEM".
TROUBLESHOOTING
Add.
Replace.
Clean.
Clean or adjust.
Adjust.
**
Disassemble or replace.
Disassemble or clean.
Resurface or replace.
Rebore or replace.
3-55
ENG