Alternators & Generators
About Alternators & Generators
An alternator or generator makes the electricity that runs a motorcycle and keeps its battery charged while the engine runs. Riders replace one when the battery will not hold a charge, when the lights dim at idle, or when they add accessories that need more output than the original makes.
The listings here are mostly kits and units for Harley-Davidson models, including alternator kits rated at 27, 29, 30 and 38 amps, 3-phase charging kits, and 6-volt and 12-volt generators, along with a Gold Wing listing. A generator is the older design, and an alternator is more common on later bikes. The amp rating shows the rated output, which should cover your electrical load. The system voltage matters too: a 6-volt unit is for a 6-volt bike. Check what the kit includes, since some add parts such as a regulator.
Brands here include Drag Specialties, Compu-Fire, Cycle Electric Inc and Rick's Motorsport Electric. Related parts are Alternator & Generator Parts and Batteries. If the bike also cranks slowly, see Starter Motor Parts. The whole group is Electrical & Ignition Components.
FAQs on motorcycle alternators and generators
What is the difference between an alternator and a generator?
A generator is the older design, producing direct current, and was common on older bikes. An alternator makes alternating current that a regulator and rectifier change to direct current. The two are not interchangeable, so match the part to your system.
Can I change a 6-volt system to 12 volts?
Changing voltage affects the battery, coil, lights, regulator and more, so it is a system change, not a part swap. Do not mix voltages. Use parts made for your bike's voltage unless you are following a full conversion kit.
What does the amp rating on an alternator kit mean?
The amp rating is the rated charging output, such as 29 or 38 amps. It should exceed what your lights and accessories draw. A higher rating suits a bike with more accessories, but the rest of the charging system has to handle it.
What is a 3-phase charging kit?
It is a charging setup that produces three-phase alternating current, which the regulator and rectifier convert to direct current for the battery. What the kit includes varies, so read the listing to see which parts are supplied.
How do I check whether my charging system works?
Use a multimeter across the battery terminals, first with the engine off and then running above idle. A higher reading with the engine running means the system is charging. Compare the figures with your service manual.
