Yamaha F50A Service Manual page 132

POWR
Check that there is no secondary air intake on the contact surfaces of
the intake manifold and crankcase.
Is there air
intake?
No
Check the compression pres-
sure of the combustion chamber.
Check the ignition spark gap using the spark gap tester.
Out of specifi-
cation?
Yes
Replace the spark plug.
5-5
Power unit
Yes
Replace the respective seals.
No
Check the ignition system out-
put peak voltage.
62Y3A11