Magneto-to-Engine External Timing

Magneto-to-Engine External Timing Adjustment

(1) Make sure the ignition is in the OFF position.
(2) Remove the engine cowl .
(3) Remove a minimum of one spark plug from each cylinder.
(4) Turn the propeller in the normal direction of movement until each impulse coupling releases as the number one cylinder moves near TDC  on the compression stroke.
NOTE: You will hear a click sound from the impulse couplings when they release.
(5) Turn the propeller in the opposite direction of normal movement to approximately 30 degrees BTDC on the number one cylinder compression stroke.
(6) Make sure that cylinder number one is at 25 degrees BTDC  on the compression stroke.
(7) Connect a standard aircraft magneto timing light between a acceptable engine ground and the P lead terminal of the magneto.
NOTE: Most standard aircraft magneto timing lights show open points with a Light On condition and/or a signal that you can hear.
(8) Loosen the mount clamps that attach the magneto to the accessory case so that the magneto will turn on the accessory case.
(9) Turn the ignition switch to the BOTH position.
(a) Look at the magneto from the aft side of the engine.
1 If the timing light is luminated, turn the magneto frame clockwise until the timing light shuts off.
2 Turn the magneto frame counter-clockwise until the timing light comes on, which shows that the contact breaker points are open.
CAUTION: Do not torque the nuts more than 17 foot-pounds (23 N-m.) or the mounting flange can crack.
(10) With the magneto set in position, first tighten each nut to 8 foot-pounds (10 N-m).
(11) Tighten each nut from one side to another, to a torque of 17 foot-pounds (23 N-m).
(12) Complete a check of the magneto timing to make sure it has not changed.