Magneto and Spark Plug Cables

NOTE

It is normally more economical to replace the

spark plugs than to clean and regap them. It

also provides greater assurance that there are

no hidden cracks in the ceramic insulators which

could cause engine misfiring at high engine

speeds. Cleaning and inspection instructions

are given here in case it is necessary to reuse

the removed plugs.

b. Cleaning and Inspection.

WARNING

Clean all parts in a well-ventilated area.

Avoid inhalation of solvent fumes and

prolonged exposure of skin to cleaning

solvent. Wash exposed skin thoroughly. Dry

cleaning solvent (fed. spec. P-D-680) used

to clean parts is potentially dangerous to

personnel and property. Do not use near

open flame or excessive heat. Flash point of

solvent is 100 to 138 F (38 to 59 C).

(1) Wipe the exterior of the spark plugs with a

cloth dampened with dry cleaning solvent (fed. spec. P-

D-680); dry thoroughly.

(2) Check the ceramic insulator for cracks,

porosity, and other damage.

(3) If the electrodes of the spark plugs are not

too badly burned, remove the scale and other deposits

from them. This can be done by a sand- blast-type

cleaner or with a contact file.

(4) Inspect the electrodes for severe burning,

cracks, and other damage. If it is necessary to reuse

the plugs, correct the contact gap to 0.025 inch.

(5) Replace any spark plugs whose condition is

doubtful.

Figure 4-20. Magneto-to-spark plug connections.

c. Installation.

(1) Make sure all spark plugs are gapped to

4-35. Magneto and Spark Plug Cables

0.025 inch before installation.

a. Removal.

(2) Install the spark plugs, using a socket and

(1) Refer to paragraph 4-24 for removal of

torque wrench. Tighten the spark plugs to 35 foot-

carburetor. Refer to paragraph 4-19 for removal of the

pounds torque.

lower panel.

(3) Install the shielded spark plug cables on the

(2) Remove the four screws (1, fig. 4-19) and

spark plugs. Make sure the leads are not interchanged.

lock washers (2) that secure the cover (3) on the

Refer to figure 4-20 to ensure proper magneto-to-spark

magneto; remove the cover and gasket (4).

plug wiring if spark plug connection is doubtful.

(3) Disconnect the shielded spark plug cables

from the magneto end cap by unscrewing

4-35