Honda EM50is Manuel De L'utilisateur page 50

4.Visually inspect the spark plug. Replace it if damaged or badly fouled,
if the sealing washer is in poor condition, or if the electrode is worn.
Clean the spark plug with a wire brush if it is to be reused.
5.Measure the plug gap with a feeler gauge.
Correct as necessary by carefully bending the side electrode.
The gap should be:
0.7–0.8 mm (0.028–0.031 in)
SIDE ELECTRODE
SEALING WASHER
6.Install the spark plug carefully by hand, to avoid cross-threading.
7.After a new spark plug has been seated by hand, it should be 
tightened 1/2 turn with a wrench to compress its sealing washer.
If a used plug is being reinstalled, it should only require 1/8 to 1/4
turn after being seated.
CAUTION:
• The spark plug must be securely tightened. An improperly tightened
plug can become very hot and possibly damage the generator.
• Never use a spark plug with an improper heat range.
8.Reinstall the spark plug inspection cover and tighten the cover screw.
48
0.7–0.8 mm 
(0.028–0.031 in)
PLUG GAP