Honda 2004 XR400R Owner's Manual page 94

2. Disconnect the spark plug cap.
3. Remove the spark plug with the multi-
purpose wrench ( ) provided with your 1
motorcycle.
4. Inspect the spark plug electrodes for wear.
The center electrode ( ) should have square
edges. The side electrode ( ) should not be
eroded. The insulator should not be cracked
or chipped.
5. Check the spark plug gap ( ), using a wire-
type feeler gauge. If adjustment is necessary,
bend the side electrode carefully. The gap
should be:
0.024 0.028 in (0.60 0.70 mm)
Make sure the plug washer is in good
condition.
If you have to install a new plug, first check
the gap.
6. With the plug washer attached, thread the
spark plug in by hand (to prevent cross-
threading).
2
3
4
7. Tighten the spark plug:
about 1/8-1/4 turn after it seats (if the old
plug is good).
about 1/2 turn after it seats (if installing a
new plug).
Improperly tightened spark plugs can damage
the engine. Too loose, you can burn a piston.
Too tight, you can damage the threads.
Spark Plug
Servicing Your Honda
85