Honda Ruckus NPS50 2018 Owner's Manual page 61

Tighten the spark plug:
6.
If the old plug is good:
●
1/8 turn after it seats.
If installing a new plug, tighten it twice
●
to prevent loosening:
a) First, tighten the plug:
1/2 turn after it seats.
b) Then loosen the plug.
c) Next, tighten the plug again:
1/8 turn after it seats.
NOTICE
An improperly tightened spark plug can damage
the engine. If a plug is too loose, a piston may be
damaged. If a plug is too tight, the threads may
be damaged.
Install the parts in the reverse order of
7.
removal.
When reinstalling the spark plug cap,
u
take care to avoid pinching any cables
or wires.
Spark Plug Changing Spark Plug
u
57