GY6 Stator with 5 cables type 139QMB / 139QMA

Function of an alternator

The ignition or alternator consists of various elements that produce a spark at the spark plug, which ignites the mixture and thus makes the engine run.

Alternators are not always electronic. Vintage mopeds like the Peugeot 103 or the Mobylette have breaker ignitions, unfortunately they wear out quickly and become easily misaligned.

Nowadays, all vehicles have electronic ignitions, which are more reliable and durable.

The ignition consists of a rotor or pole wheel, a stator with the ignition coils, a wiring harness and a CDI. We won't go into too much technical details here, but the ignition, which is attached to the crankshaft, generates an AC voltage with the crankshaft rotating. This voltage is passed to a capacitor, which stores this energy to pass it on at the right time to the coil, which acts as a transformer to make the spark plug produce a spark.

Simply put, the ignition generates the electrical energy needed for the plug to produce a spark, which in turn causes the mixture to explode.

Ignition Performance

While most 50cc motorcycles and scooters are equipped with alternators that generate the power for the vehicle's lighting in addition to the energy for the spark, there are also racing ignitions like those found on motocross machines.

Performance can be improved very effectively via the ignition. By changing the ignition timing, you can optimize the engine's performance, but you should have the required know-how to do so.
The weight of the rotor can also affect engine performance. A lighter rotor will allow for a quicker increase in rpm, while a heavier rotor can help improve torque.

On 50cc motorcycles and scooters, you can change the ignition with a simple offset woodruff key, or you can buy for an internal rotor ignition. Most racing ignitions with an internal rotor also have a CDI with variable ignition timing, which maintains high torque at low rpm and maximum power at high rpm, as the explosion always occurs at the optimum time.

Removing and Installing an Alternator

To remove and reinstall the ignition, you will need special tools:

• For disassembly you need a flywheel puller to remove the magnetic rotor.
• When reinstalling the ignition you need a micrometer to adjust the ignition.

Here is a detailed tutorial to help you install an internal rotor ignition.