2006-2014 Honda FourTrax ATV TRX250 EX TRX250X Service Manual, Page 61Get this manual
MAINTENANCE Check the following and replace if necessary (recommended spark plug: page 4-2) insulator for damage electrodes for wear burning condition, coloration;dark to light brown indicates good condition- excessive lightness indicates malfunctioning ignition system or lean mixture- wet or black sooty deposit indicates over-rich mixture,
CENTER ELECTRODE SIDE ELECTRODE
INSULATOR
Clean the spark plug electrodes with wire brush or special plug cleanerCheck the gap between the center and side electrodes with wire-type feeler gauge, If necessary, adjust the gap by bending the side electrode carefully SPARK PLUG GAP: 0.80.9 mm (0,030.04 in)
To prevent damage to the cylinder head, hand tighten the spark plug before using wrench to tighten to the specified torque