Motorcycle Alternator & Charging Parts

The charging system of a typical motorcycle consists of several parts, including an alternator or generator (magneto), battery, rectifier/voltage regulator, fuses, and wiring. The system is designed to generate electrical power that can be stored in the battery and used to power all of the electrical components of the bike. A motorcycle alternator produces an alternating current that needs to be rectified or transformed into a direct current to be stored in the battery. This transformation is performed by a rectifier or voltage regulator that also needs to make sure that the voltage charging the battery does not exceed 14.5 Volts.

Some models of vintage motorcycles were equipped with DC generators that produced enough energy to power the ignition, headlights, taillights, and horns. When bikes became more advanced, with lots of electrical equipment, such as a starter motor, turn signals, electronic fuel injection, and so on, motorcycle manufacturers switched to alternators. The majority of modern motorcycle alternators consist of thee separate pieces – a stator, rotor, and external voltage regulator. If needed, each of these components can be serviced separately. Some models of heavy touring motorcycles can be equipped with heavy-duty alternators designed as stand-alone units. They are mounted separately from the engine and driven by chains or gears from the crankshaft.

The rotor of a standard motorcycle alternator is mounted directly to the end of the crankshaft. Usually, it looks like a small wheel with powerful magnets mounted on it. Less commonly, instead of permanent magnets, rotors are equipped with electromagnets. The stator consists of a series of copper wire coils wound on iron poles. An alternator may utilize from one to a dozen such assemblies depending on the required output. Various designs feature external or internal architecture where magnets can revolve around or inside the stator coils. Any alternator uses electromagnetic induction to produce electricity – while spinning, magnets on the rotor induce an electrical current in the coils. In some motorcycle models, the alternator’s rotor also performs the role of a flywheel.

Since all electrical equipment of a motorcycle runs on direct current, the alternator’s output needs to be rectified and stabilized. A voltage rectifier or regulator transforms the alternating current coming from the alternator into direct current that can be stored in the battery. Modern rectifiers are based on series of semiconductor diode bridges that transform AC into DC. During its operation, the device produces heat that needs to be dissipated into the atmosphere. That is why motorcycle rectifiers/regulators usually come in finned aluminum cases and are exposed to the cooling air stream.

To check if the alternator of your bike works properly, you need to use a multimeter. First, test the voltage on the battery when the engine is off, then start the engine and measure the voltage again. The second figure must be higher and measure around 14.5 Volts. If you don’t have a multimeter, you can assess the voltage visually by turning on the headlight when the motor is not running. After starting the engine, twist the throttle. If the light becomes a bit brighter, your alternator produces additional power to recharge the battery. To find all parts and components that you may need for replacement, browse our online catalog of motorcycle alternator and charging parts.