Spark Plug: Testing and Inspection

REMOVAL AND INSTALLATION

CAUTION: All spark plugs installed on an engine, must be of the same heat range.

Spark Plugs: Champion: R1OYC4
(Alternates): NGK: BKR6E-11, Nippondenso: K2OPR-U1, Champion: RC8YC4

1. Remove spark plug cords by pulling boot, not cord.
2. Remove spark plugs.
3. When installing spark plugs on cylinder head, use spark plug wrench.

Torque: 20.6 ± 2.9 N.m (15.19 ± 2.14 ft-lb)

CAUTION: The above torque should be only applied to new spark plugs without oil on their threads. If the threads are lubricated, the torque should be reduced by approximately 1/3 of the specified torque in order to avoid over-stressing.

4. Connect Spark Plug cords.





INSPECTION
Check electrodes and inner and outer porcelain of plugs, noting the type of deposits and the degree of electrode erosion.





1. Normal.
Brown to grayish-tan deposits and slight electrode wear indicate correct spark plug heat range.





2. Carbon Fouled.
Dry fluffy carbon deposits on insulator and electrode are mostly caused by slow speed driving in city, weak ignition, too rich a fuel mixture, dirty air cleaner, etc. It is advisable to replace with plugs having hotter heat range.





3. Oil Fouled.
Wet black deposits show excessive oil entrance into combustion chamber through worn rings and pistons or excessive clearance between valve guides and stems. If same condition remains after repair, use a hotter plug.





4. Overheating.
White or light gray insulators with black or gray brown spots and bluish burnt electrodes indicate engine overheating, incorrect ignition timing, loose spark plugs, wrong selection of fuel, hotter range plug, etc. It is advisable to replace with plugs having a colder heat range.





CLEANING AND REGAPPING
Clean spark plugs in a sand blast type cleaner. avoid excessive blasting. Clean and remove carbon or oxide deposits, but do not wear away porcelain. If deposits are too stubborn, discard plugs. After cleaning spark plugs, recondition firing surface of electrodes with a file. Then correct the spark plug gap using a gap gauge.

Spark plug gap: 1.0 - 1.1 mm (0.039 - 0.043 in)