ENGINE RUNS BUT CONTINUALLY MISFIRES.

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

ENGINE-Continued

Step 6. Check magneto breaker points for proper gap.

a. Remove four screws and lockwashers that secure the end cover on the magneto; remove the cover and gasket.

b. Tag and disconnect the shielded spark plug cables from the magneto end cap, by unscrewing the shield

connectors.

c. Using the hand crank, turn the engine over until the moveable contact is on the high portion of the cam. Insert a

feeler gage between the contact points. The required contact gap is 0.015 inch. Loosen the stationary contact

mounting screw and adjust the position of the stationary contact to provide the required gap when the cam holds

the contacts fully open. Tighten the stationary contact screw, to secure the adjustment.

Step 7. Check carburetor fuel filter.

WARNING

Dry cleaning solvent, PD-680, used to clean parts is potentially dangerous to personnel

and property. Avoid repeated and prolonged skin contact. Do not use near open flame or

excessive heat. Flash point of solvent is 100F-138F (38C-59C).

a. The carburetor fuel filter is located in top of the carburetor near the fuel inlet.

b. Remove the fuel filter from the carburetor.

c. Clean fuel filter with a soft bristle brush and dry cleaning solvent (fed. spec PD-680). Allow filter to dry

thoroughly before reinstalling.

Step 8. Check for defective spark plugs.

a. Tag and disconnect the shielded spark plug cables from the spark plugs. Using a spark plug wrench, Remove

the spark plugs.

WARNING

Dry cleaning solvent, PD-680, used to clean parts is potentially dangerous to personnel

and property. Avoid repeated and prolonged skin contact. Do not use near open flame or

excessive heat. Flash point of solvent is 100F-138F (38C-59C).

b. Wipe the exterior of the spark plugs with a cloth dampened with dry cleaning solvent (fed. Spec. PD-680) dry

thoroughly.

c. Check the ceramic insulator cracks, porosity, and other damage.

d. 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.

e. Inspect the electrodes for severe burning cracks, and other damage. Replace any spark plugs whose condition

is doubtful.

f. Make sure all spark plugs are gapped to 0.025 inch before installation. Install and torque the spark plugs to 35

foot pounds.

Step 9. Check for incorrect ignition timing.

a. Start the engine and idle at 600 rpm.

b. Use a timing light, connected to the rear spark plug and check that the IGN-M indication on the flywheel is

aligned with the timing pointer. If it is not aligned, loosen the magneto mounting hardware and rotate the magneto

slightly until the IGN-M indication on the flywheel is obtained.

4. ENGINE RUNS BUT CONTINUALLY MISFIRES.

Step 1. Check for water in fuel.

Drain fuel tank and lines. Refill with fresh fuel.

Step 2. Check for clogged fuel strainer.

a. Close the shutoff valve on fuel strainer.

b. Loosen the bail nut and swing the bail aside. Remove the glass bowl and gasket. Empty the contents of the

bowl and wipe it dry with a clean dry cloth.

c. If engine operation indicates that the filter element is contaminated, replace it with a new one.

d. Install filter element in strainer housing, and install gasket and glass bowl. Swing bail into position and tighten

the bail nut.

Step 3. Check carburetor fuel filter.

WARNING

Dry cleaning solvent, PD-680, used to clean parts is potentially dangerous to personnel

and property. Avoid repeated and prolonged skin contact. Do not use near open flame or

excessive heat. Flash point of solvent is 100F-138F (38C-59C).

a. The carburetor fuel filter is located in top of the carburetor near the fuel inlet.

b. Remove the fuel filter from the carburetor.

c. Clean fuel filter with a soft bristle brush and dry cleaning solvent (fed spec PD-680). Allow filter to dry

thoroughly before reinstalling.

Step 4. Check for defective spark plugs.

a. Tag and disconnect the shielded spark plug cables from the spark plugs. Using a spark plug wrench, remove

the spark plugs.

WARNING

Dry cleaning solvent, PD-680, used to clean parts is potentially dangerous to personnel

and property. Avoid repeated and prolonged skin contact. Do not use near open flame or

excessive heat. Flash point of solvent is 100F-138F (38C-59C).

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