Yamaha FT50C Service Manual page 246

TRBL
SHTG
Symptom: Engine cranks, but will not start.
• Check the ignition system.
• Check the fuel system.
• Check the compression pressure of power unit.
Check the ignition spark using the spark gap tester.
Below the
spark gap
specification?
No
Check the condition of the spark
plugs.
Wet spark
plugs?
Yes
Start the engine using dried or
new spark plugs.
Does the
engine start?
Yes
Check the condition of the spark
plugs again.
Wet spark
plugs?
Yes
Check the fuel system.
9-3
Troubleshooting
Yes
Check the ignition system
output peak voltage.
No
Check the fuel system.
No
Check the compression pres-
sure of the combustion chamber.
Failure in starting operation
No
Failure in starting operation
Out of specifi-
cation?
No
Adjust the valve
clearance.
WARNING
• Do not touch any of the
connections of the spark
gap tester leads.
• Do not let sparks leak out
of the removed spark
plug caps.
• Keep flammable gas or
liquids away, since this
test can produce sparks.
Yes
Check the valve
clearance.
Yes
Out of specifi-
cation?
No
Check the cylinder head, cylin-
der body, and piston assembly.
62Y5A11