Onan NHC Series Operator's/Service Manual And Parts Catalog page 293

IGNITION SYSTEM
BREAKER POINTS
To maintain maximum efficiency from the engine,
change the breaker points every 200 hours of opera-
tion. Proceed as follows:
1. Remove the two screws and the cover on the
breaker box.
2. Remove the two spark plugs so engine can be
easily rotated by hand. If plugs have not been
changed within the last 100 hours, replace them
with new ones after setting the breaker points.
3. Refer to Figure 22. Remove mounting screw (A)
and pull the points out of the box just far enough
so screw (B) can be removed and leads dis-
connected.
4. Remove screw (C) and replace condenser with a
new one.
5. Replace points with a new set but do not com-
pletely tighten mounting screw (A).
6. Rotate the engine by hand until the20° BTC mark
on gear cover aligns with mark on flywheel. Turn
another 1/4 turn (90° ) to ensure points are fully
open.
7. Using a screwdriver inserted in notch (D) on the
right side of points, turn points until gap
measures .016-inch with a flat thickness gauge.
Tighten mounting screw and recheck gap.
8. Check ignition timing.
MOUNTING SCREWS
FIGURE 22. BREAKER POINT ADJUSTMENT
TIMING P R E S S U R E C O O L E D ENGINE
The timing on the engine is preset at the factory. A
non-movable breaker point box is used, however a
slight timing change could be made by adjusting
points.
The engine is equipped with an automotive type
battery ignition system. Both spark plugs fire
simultaneously, thus the need for a distributor is
eliminated. Spark advance is set at 20° BTC (before
top center), and should be maintained forbest engine
performance. Always check timing after replacing
ignition points or if noticing poor engine perfor-
mance. Proceed as follows:
Timing Procedure—Engine Running:
1. To accurately check the ignition timing, use a
timing light with engine running at idle speed.
Connect the timing light according to its
manufacturer's instructions. Either spark plug
can be used as they fire simultaneously.
2. Start theengine and check the timing. The pointer
on the flywheel should line up with the 20° mark
on the cover. The timing hole through the
flywheel and the timing marks on the timing gear
cover can be seen by looking through -the
flywheel blower screen. See Figure 23.
if timing marks do not line up, readjust point gap. To advance
timing, slightly open gap on breaker points. To retard timing,
slightly close gap on breaker points. Recheck timing and
breaker point gap after making this adjustment.
Timing Procedure—Engine Not Running: If a timing
light is not available, check the timing as follows:
1. Connect a continuity test lamp set across the
ignition breaker points. Touch one test prod to
the breaker box terminal to which the coil lead is
connected and touch the other test prod to a good
ground on the engine.
2. Turn crankshaft against rotation (coun-
terclockwise) until the points close. Then slowly
turn the crankshaft with rotation (clockwise).
3. The lamp should go out just as the points break
which is the time at which ignition occurs
(20° BTC).
POINTER ON TIMING
HOLE IN F L Y W H E E L
F L Y W H E E L
FIGURE 23. FLYWHEEL TIMING HOLE
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