Magneto-to-Engine Timing Check

A. Complete a Check of the Magneto-to-Engine Timing.
(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) Connect a standard aircraft magneto timing light between an acceptable engine ground and the P lead terminal of the magneto.
NOTE: Most standard aircraft magneto timing light indicate open points with a Light On condition and/or an signal that you can hear.
(5) Turn the ignition switch to the BOTH position.
(6) Turn the propeller in the normal direction of movement until each impulse coupling releases as the number one cylinder moves near TDC (Top Dead Center) on the compression stroke.
NOTE: You will hear a click sound from the impulse couplings when they release.
(7) Turn the propeller in the opposite direction of normal movement to approximately 30 degrees BTDC (Before Top Dead Center) on the number one cylinder compression stroke.
(8) Slowly turn the propeller in the normal direction of movement until the timing light comes on.
(9) Examine the crankshaft to make sure it is in the correct position.
NOTE: The timing light must come on at 25 degrees BTDC with the number one cylinder on the compression stroke.
(10) If the crankshaft is not in the correct position you will have to make an adjustment. Refer to Magneto-to-Engine External Timing Adjustment .
(11) Turn the ignition switch to the OFF position.
(12) Install the spark plugs.
(13) Install the ignition leads on the spark plugs.
(14) Install the cowl. Refer to Chapter 71, Engine cowl - Maintenance Practices .
(15) Complete a engine preflight operational check of the ignition system.