WM 80 repair Starting and Ignition
wc_tx000521gb.fm 37
4.7 Ignition System Operation
See Graphic: wc_gr002883
The ignition system consists of the ignition module (a), flywheel (b),
shutoff switch (c) or (d), and spark plug (e).
During each engine revolution, a permanent magnet (f) embedded in
the flywheel passes under the ignition module. As the magnet passes
the module, it induces a current in the primary side of the coil. After it
passes, the triggering circuit is activated and the current flow to the coil
is interrupted. The resulting collapse of the magnetic field around the
coil secondary causes a voltage discharge to fire the spark plug.
Older Ignition Systems
Spark is provided by a breakerless electronic Transistor Controlled
Ignition (TCI). There are no breaker points or capacitors. The ignition
module is completely self-contained and fully enclosed. It includes the
ignition coil and triggering circuit. Two different modules are used. The
standard module (aa) is used in all applications except for rammer
models BS62Y and BS65Y. On these models an ignition module (aaa)
with speed limiter is used. This module cuts out ignition pulses at
higher speeds to keep the engine from running away. The two modules
are not interchangeable. Note the physical differences as shown. The
speed limiting module has an extra coil (g) and a yellow ground wire.
The standard module has no extra coil and a blue ground wire.
NOTICE: Do not use the standard module on the BS62Y or the BS65Y
rammers. Engine damage will occur.
Newer Ignition Systems
Starting with Rammer Models BS 500 and BS 600 (including models
with oil-injection) and carrying through to current Rammer Models BS
50-2 and BS 60-2 (also including models with oil-injection) a
microprocessor-based ignition system is used. This retarding-type.
ignition alters the timing (advance or retard) of the spark to match the
load.
Two different styles of engine shutoff switches are used. One is a stop
switch (c) located on the engine housing (breakers, plates). The other
is a fuel/shutoff switch (d) located under the fuel tank (rammers). This
switch cuts power to the engine and closes the fuel valve. Both styles
of shutoff switches are normally open and when activated create a
short circuit directly to ground. The short circuit prevents the plug from
firing and thus stops the engine.
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