Ignition System; Crankshaft Position Sensor; Throttle Position Sensor; Engine Coolant Temperature Sensor - Cagiva Navigator Workshop Manual

IGNITION SYSTEM

DESCRIPTION
The ECM CPU controls the ignition system. It is a normal transistorised digital ignition system that determines
precise ignition timing according to the rpm of the engine, the gearchange position and the throttle position.
The system consists of a crankshaft position sensor (explorer coil), an ECM CPU, two ignition coils and two spark
plugs.
1. The ignition coil feed is supplied by the battery via the side stand relay. This means that the ignition coil feed is
controlled by the side stand position switch and the gearchange position switch.
2. The timing of the ignition is precisely controlled by the rpm of the engine and the throttle position. Apart from this
basic condition, also the engine coolant temperature sensor influences the ignition timing when the temperature
of the engine coolant is low and when the engine is switched on from cold by utilising the choke.
3. Ignition timing changes according to the gearchange position and the position of the throttle.
To switch the ignition system on or off, the following devices influence the ignition timing.

Crankshaft position sensor:

On the extreme left hand side of the crankshaft there is an explorer coil that produces a form of electrical wave
when it comes into contact with the projection of the generator rotor.
The form of electrical wave generated is sent to the ECM CPU that calculates the rpm of the engine.
This signal determines the ignition timing and the signal that is sent to the revcounter.
This signal determines the ignition timing without calculating the signals under 700 rpm, because the rotation
speed of the engine is constantly changing at low revolutions.
Above 700 rpm, the signal is processed by the ECM CPU and calculates the ignition timing with regards to the
choke setting and the temperature of the engine coolant.
When the engine is switched on, the timing is calculated at 1° ATDC until 700 rpm.
If this signal is not sent to the ECM CPU, the ignition and injection systems do not function.

Throttle position sensor:

This sensor is situated in the carburettor and is a type of variable resistance sensor that changes the value of the
resistance when the throttle is opened. On the basis of the signal received, the ECM CPU determines the ignition
timing of the throttle by rpm of the engine.
The ignition conditions are determined by two factors: the throttle position and the rpm of the engine.
Gearchange position switch:
The gearchange position switch possesses a different resistance for each gear so that the ECM CPU is capable of
determining the position of the gearchange. The ECM CPU varies the ignition timing when the position of the
gearchange varies.

Engine coolant temperature sensor:

This sensor advances the ignition timing when the temperature of the engine coolant is less than 60°C. and when
the choke functions with the butterfly valve closed.
The timing is advanced during the choke operation and gradually returns to normal when the temperature of the
engine coolant increases.
ELECTRICAL EQUIPMENT
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G.21