Onan NHC Series Operator's/Service Manual And Parts Catalog page 294

TIMING VACU-FLO ENGINE
Engine timing is advanced or retarded by opening or
closing the breaker point gap. Setting the point gap at
0.016 inch is the most accurate method of timing the
engine.
Dynamic timing (engine running) may be less ac-
curate because the sight angle from the viewer to the
flywheel scribe mark and timing pointer may vary ± 2°
from 20° BTC, Figure 24.
The timing pointer is mounted on the cylinder block
above the oil filter; it is made accessible by removing
the right hand shroud.
OIL F I L T E R
IGNITION COIL
To test primary and secondary windings within the
ignition coil proceed as follows:
1. Use Simpson 260 VOM or equivalent.
2. Place black lead on ground (-) terminal of coil and
red lead to positive (-) terminal. Primary
resistance should read 4.30 (± 10%) ohms @
70° F.
3. Change resistance setting on ohmmeter. Place
ohmmeter leads inside of spark plug cable holes
(Figure 26). Secondary resistance should read
14,000 (±10%) ohms @ 70° F.
4. if any of theaboveconditionsarenotmet, replace
coil. Refer to Parts Catalog for correct part
• number.
This engine uses a 12 volt, negative ground
system. Alternator must be connected to
battery at all times when engine is running. Do not reverse battery
cables.
L _ O H M M E T E P
20" STC MARK
ON F L Y W H E E L
FIGURE 24. VACU-FLO ENGINE—TIMING
MARK AND POINTER
SPARK PLUGS
Remove both spark plugs and install new ones every
100 hours. Use Onan spark plugs 167-0240 or
equivalent. Check to be sure spark plug gap is set at
.025 inch, Figure 25.
SPARK PLUG GAP
0.02S" GASOLINE
FIGURE 26. COIL TEST
BATTERY INSPECTION
Check battery cells with a hydrometer. The specific
gravity reading should be approximately .1.280 at
80° F, Figure 27.
S P E C I F I C
G R A V I T Y R E A D I N G
, S H O U L D B E
S 1 . 2 8 0 A T 80= F.
FIGURE 25. SPARK PLUG GAP
FIGURE 27. SPECIFIC GRAVITY TEST
25
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