Digitally Controlled Transistorized Ignition System - Honda Motorcycle Service Manual

IGNITION SYSTEMS
As the engine speed increases, the duration of current
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flowing through the primary coil becomes shorter and
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eventually thesecondary coil voltage is not high enough.
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The ianition timina control circuit also controls the duration
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DURATION
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of current flow through the ignition primary coil to ensure
IGNITION PRIMARY
the correct plug-firing voltage to the secondary coil.
COIL VOLTAGE
DIGITALLY CONTROLLED TRANSISTORIZED IGNITION SYSTEM
This system digitally controls the ignition timing using a microcomputer inside the ignition control module which
calcuiates the ideal igniton timing at all engine speeds. The microcomputer also hasa fail-safe mechanism which cuts off
power to the ignition coil(s) in case the ignition timing becomes abnormal.
The system consists of an ignition pulse generator rotor, one or t w o ignition pulse generators, the ignition control
module, ignition coil(s), and spark plugls).
1) The ignition pulse generator rotor has projections called reluctors that rotate past the ignition pulse generatorb),
producing electronic pulses which are sentto the ignition control moduleThe engine rpm and crankshaft position of each cylinder
are detected by the relative positions of the projections of the ignition pulse generator rotor(s).
2) The ignition control module is non-serviceable and consists of a power distributor, a signal receiver, a microcomputer
and a distributor.
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The power distributor distributes battery voltage to the ignition control module when the key is turned on.
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The signal receiver receives the electronic pulse from the ignition pulse generatorb) and then converts the pulse
signals to a digital signal. The digital signal is sent t o the microcomputer which has a memory and an arithmetic unit.
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The microcomputer memory stores the desired characteristics of the timing for each rpm and crankshaft position. The
arithmetic unit relays the rpm and crankshaft position to microcomputer memory.
The memory then determines when to turn the transistor o n and off t o achieve the correct speak plug firing time.
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When the transistor is turned on the primary coils of the ignition coils are saturated. Memory then turns the transistor
off when
it
is time to fire the spark plug.
The system illustration below features a simplified single ignition pulse generator rotor system. This type is used on many
models produced from early 1989 onward. Dual ignition pulse generator systems are very similar in design and are found
o n most engines produced before this time.
IGNITION ENGINE
PULSE GENERATOR
STOP SWITCH IGNITION SWITCH
ROTOR
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BATTERY
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SPARK PLUG
GENERATOR
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CONTROL
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BATTERY
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COIL
IGNITION SPARK PLUG
P l l l SF
MODULE
23-8
Date of Issue: March. 1995
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HONDA MOTOR CO.,LTD.