Magneto - TM-5-4320-259-120040

(6) Remove the screws (9) and lock washers

b. Cleaning and Inspection.

(10) that secure the magneto frame to the engine

(1) Wipe carbon and other deposits from the

bearing plate; remove the magneto frame.

spark plug terminals. Clean the remainder of the

c. Cleaning and Inspection.

plug with a cloth dampened with an approved

(1) Wipe the magneto coil and capacitor with

cleaning solvent; dry thoroughly.

a cloth dampened lightly with an approved cleaning

(2) Wipe the spark plug cable with a cloth

solvent; dry thoroughly. If contact points are dirty,

lightly dampened with solvent. Take care not to

burnish them with fine sandpaper.

saturate the parts.

(3) Inspect the spark plug for burned ter-

(2) Clean the magneto frame with an ap-

proved cleaning solvent; dry thoroughly.

minals, defective insulator, and damaged threads.

(3) Inspect the magneto coil for obvious

If the spark plug is in good condition, regap it to

defects which could result in damaged windings,

0.020 inch. If terminals are corroded or pitted,

and for cracks, deterioration of insulation, and

replace the plug.

damaged electrical connections. Continuity of the

(4) Inspect the spark plug cable for damaged

coil can be checked with a test lamp. Check con-

shielding, cracked or deteriorated insulation,

tinuity across the primary terminals to check the

damaged connector threads, or other damage;

primary circuit. The test lamp should light when

replace a damaged spark plug cable.

connected in series with the primary circuit. To

c. Installation.

check the secondary circuit, connect the test lamp

(1) Install the spark plug (1, fig. 4-3) and

from the secondary terminal to one of the primary

gasket (2) on the cylinder head. Torque the spark

terminals. The test lamp will not light, but con-

plug to 27 foot-pounds.

tinuity will be indicated by small sparks as the leads

(2) Connect the threaded end of the cable (4)

are rubbed across the terminals. Replace an open

to the spark plug. Connect the opposite end of the

magneto coil.

cable by inserting the cable end into the socket of

(4) Check the capacitor with a capacitor

the magneto coil (5). Connect the shielding of the

checker if available. If a capacitor checker is not

cable to the magneto frame.

available, the capacitor can be checked with an

(3) Install the flywheel and starter pulley on

ohmmeter. When the ohmmeter is connected across

the end of the crankshaft (para 4-13 c). Install the

the terminal and the capacitor case, low resistance

blower housing (para 4-12 c).

should be indicated momentarily, followed by a

4-16. Magneto

h i g h resistance indication. Continued low

a. Testing. Check the operation of the magneto

resistance indicates a shorted capacitor.

as follows:

(5) Faulty operation of the magneto can be

(1) Disconnect the spark plug cable from the

caused by the loss of residual magnetism of the

spark plug and hold the end terminal about 1/16

permanent magnets of the flywheel. A rough check

to 1/8 inch away from the cylinder head while

of the magnetic force can be made by placing the

cranking the engine with the starting rope. Make

flywheel, open end up, on the work bench and

sure the engine is cranked fast enough to produce a

suspending a nonmagnetized steel screwdriver

good spark.

between the thumb and forefinger, point down.

(2) A hot spark should jump the gap between

Move the point to within one inch of the magnets

the terminal and the cylinder head. If a sharp,

cast in the flywheel. The magnets must be strong

snappy spark is observed, it indicates that the

enough to attract the screwdriver, pulling it against

magneto, capacitor, and breaker points are in good

the flywheel. If the magnetism is insufficient,

condition.

replace the flywheel.

b. Removal.

d. Installation.

(1) Remove the blower housing from the

(1) Installation is the reverse of removal.

engine (para 4-12 a) and remove the starter pulley

Refer to figure 4-3. Be sure that good contact is

and flywheel (para 4-13 a).

made at all electrical connections.

(2) Disconnect the spark plug cable (4, fig. 4-

(2) Install the flywheel and starter pulley

3) from the magneto coil (5). Disconnect the

(para 4-13 c) and install the blower housing (para

primary lead from the magneto capacitor (8).

4-12 c).

(3) Slide the magneto coil (5) from the

4-17. Breaker Points

magneto frame (11).

(4) Remove the screw (6) and remove the

a. Adjustment.

primary lead from the capacitor.

(1) Remove the two machine screws (1, fig. 4-

(5) Remove the screw (7) and remove the

4) and remove the breaker cover (2) and gasket (5).

capacitor (8) from the magneto frame.

4-8