Harley 32E Generator Rebuild and 2-Brush Conversion
The Harley-Davidson 32E generator was used on V-series models and early Knuckleheads, making it a critical part of the charging system on prewar big twins. This article covers a complete 32E generator rebuild along with a 2-brush conversion, showing both the rebuild process and why the conversion can improve charging performance for real-world riding.
For more V-series technical articles, see the VL Tech section.
The Harley-Davidson V-series engines began using the Model 32E 3-brush generator in 1932. I planned to use a rebuilt 32E on my own build and started looking for a reputable builder who could supply a complete unit, since I did not have a usable core to start with. After some searching, I found Perry Ruiter in Canada. I sent him a short note explaining what I needed and how I intended to use the motorcycle, and he quickly recommended one of his rebuilt 32E units converted to a 2-brush setup. He not only explained the differences between the 3-brush and 2-brush systems, but also photographed the entire rebuild process step by step.
Why Convert a 32E to 2-Brush?
So why convert a perfectly good 3-brush generator to a 2-brush setup? As shown in the chart below, a 2-brush generator starts charging earlier, reaches full output faster, and does not fall off as speed increases. More importantly, a 2-brush system automatically matches output to demand. If the battery needs a charge, output rises until it is charged and then falls back. Turn the lights on and output increases; turn them off and it drops again. With a 3-brush generator, the third brush sets the charge rate and you are stuck with whatever you dial in.
The other big advantage to a 2-brush conversion is the ability to run a sealed battery. A 3-brush system relies on the battery for crude voltage regulation, which means voltage can swing all over the place. A modern sealed battery needs stable regulation, which is provided by a solid-state regulator. You might get away with a sealed battery in a 3-brush system if all you ever do is ride around the block once a month, but sustained highway riding is much harder on the battery. In some cases, that kind of charging instability can destroy it. A sealed battery simply does not tolerate a 3-brush charging system as well as a properly regulated 2-brush setup.
Here is the rebuild and 2-brush conversion process step by step.
Commutator End Assembly
The generator assembly starts with the commutator end casting and brush holders. Colony's terminal kit is used along with their generator frame screws. Perry swaps out the star washers for parkerized ones and uses custom-made brush holder insulating papers that are correct. Fresh cadmium plating, parkerizing, and glass beading provide the proper finishes. New fillister-head screws, a quality sealed Japanese bearing, and a NOS bearing shield washer round out the assembly.
Once the brush holders are installed, he checks to make sure the negative brush holder is grounded and that both terminals are isolated from each other and from the end casting while still maintaining continuity with their respective brush holder and terminal. Note that the multimeter is set to ohms for checking continuity and resistance.
The completed commutator end casting assembly is then set aside until final assembly.
Field Coils and Generator Body
Here is the generator body with field coils and pole shoes. Because this generator is being converted to 2-brush, the field coils are from a 1958–1964 Panhead generator supplied by Eastern Motorcycle Parts. You can also convert to 2-brush using stock 32E field coils by changing how they are connected. See Harley Service Bulletin 418 for details. Pole shoe screws also come from Colony. There is a quality sealed Japanese bearing at the drive end, and the generator body itself is a later case that accepts the neoprene seal, a style used in the last few years of Knucklehead production and into the Panhead era. It is a subtle upgrade that remains invisible once installed.
Because the field coils were originally intended for a later generator, he changed the terminals and extended one lead before installing them in the 32E body.
He then snugs up the pole shoes using a Snap-On impact driver with a custom-shaped screwdriver tip from Brownells. That lets him get the pole screws dead tight without damaging the screw heads.
Final Assembly
Now the generator is ready for final assembly. The gear, spring, and oil deflector are supplied by Eastern Motorcycle Parts. The new brushes and reproduction armature come from Dixie Distributing. Perry also made a batch of the armature bakelite washers so they would be the correct size.
When installing the roll pin in the gear, he uses a custom-made bench block to support the armature and keep it from being bent. Most reproduction gears use a 3 mm hole instead of 1/8 inch, so he uses 3 mm roll pins. In the photo above, you can also see that the generator body is parkerized before painting, which helps prevent rust if the paint gets chipped or scratched.
Once the generator is fully assembled, a battery is hooked up to motor it. The generator should turn counter-clockwise when viewed from the gear end. If it rotates the other way, the field coil leads are reversed. This verifies correct assembly and also provides the initial polarization of the pole shoes. The generator relies on residual magnetism in the pole shoes for initial excitation at startup.
Recall that the 32E was converted from a 3-brush generator to a 2-brush generator. In the photo above, the third brush holder sits empty in the assembled unit.
Regulator and Load Testing
Since the generator has been converted to 2-brush, a regulator is required. A solid-state Vtronic 6-volt regulator supplied by RetroCycle is the natural choice, and it is also available in 12 volts. Unfortunately, the manufacturer only supplies this unit in a 1938–1957 three-post style, so Perry modifies the Vtronic regulator to retain the correct two-post outward appearance for the VL series while hiding the third post underneath.
Although he has a Sun generator and alternator test bench, he still has a strange affection for an older generator tester rescued from a Harley dealer years ago. The generator is run at speed and tested under load with a Cycleray headlight while output is monitored using a multimeter set to amps. This confirms that the regulator and generator respond correctly as load is applied and removed.
To finish things out, he added a cover on the regulator, a nice old original tag, and a period aftermarket chrome cover to complete the generator. At that point, it was ready for service.
Parts Sources
Colony Machine
30012-32 Generator Screws
2126-12 Terminal Kit
9520-4 Pole Screws
Eastern Motorcycle Parts
A-31035-31 Oil Deflector
A-31070-30 Generator Gear
A-31040-31 Spring
E-1007 Field Coils
RetroCycle
0478506 Vtronic 6-Volt Regulator
Dixie Distributing
Brushes
Armature
Upgrade Summary
This rebuild and 2-brush conversion makes the 32E generator more practical for real riding by improving charge control, allowing use of a proper solid-state regulator, and making sealed-battery setups more realistic. At the same time, it preserves the correct early appearance of the generator, which is exactly the kind of upgrade that fits a rider-focused vintage build.