Yamaha KODIAK ULTRAMATIC YFM400FA Owner's Manual page 324

a. Spark plug gap
a. Écartement des électrodes
a. Huelgo de la bujía
Do not attempt to diagnose such problems
yourself. Instead, take the ATV to a Yamaha
dealer. You should periodically remove and in-
spect the spark plug because heat and deposits
will cause the spark plug to slowly break down
and erode. If electrode erosion becomes exces-
sive, or if carbon and other deposits are exces-
sive, you should replace the spark plug with
the specified plug.
Specified spark plug:
DR8EA (NGK)
8-67