The alternator which is fitted as standard is a three phase Alternating
current type, with inbuilt regulator and rectification diode pack.
The regulator does as it says it regulates the amount of power
available to the charging of the battery, whereas the diode pack
rectifies the AC source to DC, which we use throughout the
How does it work.
The basic principle of how an alternator works. The
alternator has two parts to generate the electrical power, the first
being the rotor windings and secondly the field windings, a small
current in the field windings causes the stator winding to produce a
much larger current. The current produced in the stator windings is
what we use for available power. This power is used in all the
electrical systems but remember this point - You only have so much
available - TAKE TOO MUCH (additional lights, CD player, GPS etc)
for a longer time and you can burn out the rectifier pack or the
field windings, don't rely on the fuse as their characteristics may
vary on the time it will blow. See the fuse section for detail
Testing the alternator
To test your alternator will require a digital multi-meter and
The test will require you to disconnect main fuse B. The
multi-meter should be capable to read AMPS and generally the meter
will have special sockets marked to read AMPS. Ensure this is the
case or borrow one from a friend that does. The red test probe
should be connected to the lower fuse terminal and the black lead
connected to the upper terminal. Ensure that the cables are not
touching the frame of the motorcycle, turn the ignition on and start
the engine, before taking readings ensure all electrical equipment -
radio, lights, accessories and fans are not running.
Do NOT DISCONNECT the cables whilst the engine is running as damage
may be caused to the alternator.
The alternator has two set points for the charging current to the
battery as follows:
At approx 900 rpm the alternator should give you an output
current on the ammeter of up to 2 Amps, at approx 1900 rpm the meter
should read more than 1.5 amps.
Turn off the engine and disconnect the leads, re-connect the fuse
and re-start the engine, now ensure that the leads in the meter are
changed to read DC volts, put the meter on a scale to read in excess
of 12 volts, normally the range should be around 50V DC. Place the
red test probe on the +ve terminal and the black test probe on the -ve
terminal of the battery, check the available voltage, it should read
in the region of 13.4 - 15.7 volts, just remember that this terminal
voltage is with no load supplied as a digital multi-meter takes
little or no current to operate it.
Now with the leads still connected turn on your head lights and
see what the voltage drops too. record this reading. now turn off
the engine and lights, re-test the battery voltage with the lights
off and with the leads still connected turn on the lights and record
the level. If it drops below 12 volts It could mean your battery is
flat or deteriorating. Have the battery tested.