73 Honda CB750 Custom Build Part 20 – Starter & Alternator

The starter on an engine is a DC motor that rotates the crankshaft of the engine to get it started. Once the engine is started, the starter must have some sort of mechanism that uncouples it from the engine or else it would spin too fast and be destroyed. Automotive starters have a built in mechanism called a bendix drive that engages and disengages the drive gear with the engine’s flywheel. Starters on motorcycles utilize a one way clutch known as a Sprag Clutch. It will allow torque in one direction only and slip in the other direction.

The alternator is a device that produces an AC electrical current when rotated. The center portion known as the rotor is an electromagnet. It rotates within an outer winding of metal and wire called a stator. Each component functions as an electromagnet with multiple north and south poles. When in rotation, these opposite poles pass by each other and produce and electrical current in their windings via magnetic induction. The AC current output then passes through a bridge rectifier which converts it into a DC current that can charge a battery.

In this week’s video I’ll take a look inside both of these components, test them, and then install them in the engine.

Keep on hackin…

About Dino

Self taught electronics and hardware hacker.
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