Magneto-To-Engine Timing Adjustment Procedure - Lycoming YO-233-B2A Maintenance Manual

YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
NOTICE: The advance timing specification in degrees is stamped on the engine data plate.
Turn the crankshaft in the direction of normal rotation until the correct advance timing mark
G.
on the starter ring gear support assembly aligns with the reference point on the engine (Figure
1 or 2).
The timing light is to indicate the magneto is firing when the timing mark on the starter ring
H.
gear support assembly aligns with the reference point on the engine (Figures 1 or 2) to ensure
that the magneto is correctly timed with the engine.
NOTICE: If there is interference from another engine component or an airframe component
that prevents correct adjustment of the magneto, remove the magneto and re-
position the drive gear in the accessory housing. Use care not to drop the dampers (if
installed) into the engine while repositioning the drive gear.
The magneto position is typically 15º to 30º above horizontal centerline.
I.
NOTICE: If the magneto-to-engine timing is out of tolerance by more than 5° refer to the
magneto manufacturer's instructions for internal adjustment and then complete the
"Magneto-to-Engine Timing Adjustment Procedure" in this chapter.
If the magneto-to-engine timing is out of tolerance by less than 5°, complete the
"Magneto-to-Engine Timing Adjustment Procedure" in this chapter.
If the magneto-to engine timing is within tolerance or after the "Magneto-to-Engine Timing
J.
Adjustment Procedure" has been completed:
(1) Remove the timing light leads from the magnetos and grounding source.
(2) Attach the P-Leads to the condenser terminal of each magneto with the nut and a new
lock washer. Torque the nut to 13 to 15 in.-lb (1.5 to 1.7 Nm).
Install the spark plug in cylinder No. 1 per the "Spark Plug Installation" procedure in Chapter
K.
74-20.
Connect the applicable ignition leads to all spark plugs per instructions in the "Ignition
L.
Harness Installation" procedure in Chapter 74-20.
Enable power to the engine.
M.
Complete the "Operational Ground Check" in Chapter 72-00 of the engine to make sure the
N.
magnetos are operating correctly.

3. Magneto-to-Engine Timing Adjustment Procedure

A. Turn the crankshaft in the direction of normal rotation until the correct advance timing mark
on the starter ring gear support assembly aligns with the reference point on the engine (Figure
1 or 2).
B. Loosen the hold-down nuts on the clamps of the magneto that is not timed with the engine.
C. Manually and slowly turn the magneto in its mounting flange in the direction opposite its
normal rotation until the timing light indicates the magneto is not firing.
D. Turn the magneto in the direction of normal rotation until the timing light indicates the
magneto is firing.
E. Torque the hold-down nuts on the magneto clamps 48 in.-lb. (5 Nm) increments, alternating
between the two nuts until both nuts are torqued to 15 to 18 ft.-lb. (20 to 24 Nm).
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February 2021
74-30
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