LYCOMING OPERATOR’S MANUAL SECTION 5
O-235 AND O-290 SERIES MAINTENANCE PROCEDURES
FIRING ORDER 1-3-2-4
Figure 5-3. Ignition Wiring Diagram (Optional)
Conventional Magneto – Hold the No. 1 lead wire spring 1/8 in. away from the frame. Turn the
gear counterclockwise vigorously through the flux lines until a strong spark occurs at the lead.
Reverse the rotation into the flux until the timing pin hole appears in the center of the vent plug
hole and insert the timing pin into the hole.
NOTE
If the crankshaft is accidentally turned in the direction opposite normal rotation, repeat the
above procedure, as accumulated backlash will make the final timing incorrect.
(2) Remove the inspection plugs from both magnetos and turn the drive shafts in direction of normal
rotation until the first painted chamfered tooth on the distributor gear is aligned in the center of the
inspection window. Being sure that the gear does not move from this position, install gaskets and
magnetos on the engine. Secure with washers and nuts; tighten only finger tight.
NOTE
In order to turn the shaft on an impulse coupling magneto, depress the pawl on the impulse
coupling with the finger.
(3) Using a battery powered timing light, attach the positive lead to a suitable terminal connected to
the ground terminal of the magneto and the negative lead to any unpainted portion of the engine.
Rotate the magneto in its mounting flange to a point where the light comes on, then slowly turn it
in the opposite direction until the light goes out. Bring the magneto back slowly until the light just
comes on. Repeat this with the second magneto.
5-3
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