12
IGNITION SYSTEM
When checking out an ignition system, start with the components that require most frequent service or
adjustment. Hard starting, roughness, low power and erratic operation are often attributed to faulty ignition.
All components must be in top condition and the ignition spark must be properly timed to maintain good
performance. If performance indicates that ignition is faulty, the first thing to do is to determine if this system
is actually at fault. A simple operational test will help determine this.
OPERATIONAL TEST
(except Solid State Ignition Models)
Remove high tension lead at the spark plug and hold end terminal about 1/16" to 1/8" away from the
cylinder head while cranking the engine. Make sure the engine is cranked fast enough to produce a good
spark. If a sharp snappy spark occurs, the trouble is apparently not in the ignition coil, condenser or breaker
points although it still could be attributed to poor condition of spark plug. If no spark or a very weak spark
occurs, ignition trouble is indicated.
SPARK PLUG
Engine misfire or generally poor operation is often caused by spark plugs in poor condition or with
improper gap setting. Always clean area around spark plug before removing to prevent dirt from falling into
engine. The first thing to do after removing a spark plug is to carefully note its condition as this is often an
indicator of the ignition trouble. Plugs fail for various reasons. Often the porcelain insulator cracks or
becomes coated with oil, carbon or other deposits. This can cause the high voltage ignition impulse to pass
from the center electrode to ground without jumping the spark gap. As an engine operates, the electrodes are
gradually burned or worn away. In time, the gap becomes so wide that the available ignition voltage cannot
jump the gap and the engine misses.
Spark Plug Service:
Every 100 hours remove plug, check condition and reset gap. Good operating
conditions are indicated if plug has light coating or gray or tan deposit. A dead white, blistered coating could
indicate overheating. A black (carbon) coating may indicate an "overrich" fuel mixture caused by clogged air
cleaner or improper carburetor adjustment. Set spark gap at .025". Tighten plug to 27 ft. lbs. torque when
installing.
BREAKER POINTS
Engine operation is greatly affected by breaker point condition and adjustment of the gap. If points are
burned or badly oxidized, little or no current will pass and as a result the engine may not operate at all, or if it
does run it is likely to miss particularly at full throttle.
Figure 7 Metal Transfer -- Breaker Points
