Yamaha F50A Service Manual page 130

POWR
Symptom: Engine cracks, 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.
5-3
Power unit
Yes
Check the ignition system out-
put 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
removed spark plug
caps.
• Keep
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,
cylinger body, and piston
assembly.
of the
flammable
62Y3A11