Yamaha MA190 Service Manual page 26

Spark plug
High tension line
Spark plug cap
Spark plug testing
WARNING
9 Make sure there is no spilled fuel out-
side the engine and that the spark plug
isn't dipped with fuel.
9 To prevent fire, keep sparks far away
from the spark plug mounting hole.
9 When testing the spark plug, never hold
the high tension line of the spark plug
and spark plug cap with wet hand.
9 If having fuel cock, turn the fuel cock to
"OFF" position, (if no fuel cock, first drain
the gasoline of the fuel tank, then, drain the
gasoline of the carburetor).
9 Remove the spark plug and spark plug cap.
9 Install the spark plug cap.
9 Turn the engine stop switch to "I" or "STOP"
position.
9 Pass negative pole (thread) of the spark
plug through cylinder cover to connect
grounding and pull the recoil starter grip to
observe the spark.
21
4-1 Troubleshooting