Board index Flathead Power-Technical Questions, Answers, and Suggestions Pans Herr Frankenstein help.

Herr Frankenstein help.

Post Tue Oct 22, 2019 10:39 am

Posts: 988
Location: Markt Einersheim, Germany

Herr Doctor and gentlemen,

As per Herr Frankenstein's suggestion, I modified a 65A generator with NOS 12 volt field coils, and with a NOS 6 volt armature.

It works, and I have it mounted on my 1958 FL project bike.

Now, the questions:

I seem to recall a thread where you can check the generators output while mounted on the bike running about 2 grand, once the A Terminal is disconnected and F terminal grounded. And a voltmeter connected to the A terminal and the other to ground.

I would like to know if this is correct, and if not,

How do I check for voltage output with the generator installed and the bike running.

It works, generator light goes off between 1000 and 1500 rpm. But the battery will never charge over 12.54 Volts. I would like to know what the generator is producing for power output.

And if I may, allow me to show my lack of experience/ I correct in my reading that to increase charging rate to the battery, I only have to bend the tab within the voltage regulator?? Please tell me that it is just that simple.

I have attached a link to the bike, and she is now licensed, insured and tagged and I have ridden her a couple of times trying to get the bugs worked out. ... 261&t=9461

Thanks for the help,


PS, now Retired, and playing with my retirement toy.

Post Fri Mar 06, 2020 11:45 am

Posts: 27
Location: Snohomish Co., WA
George, I don't know if you've figured this out, but if not, here goes. I have a book by Tracy Martin, "Motorcycle Electrical Systems." In the section on DC generators, he says,
To full field a generator, start the engine and hold rpm at 2000. Connect an inductive amp probe around the wire at terminal A of the voltage regulator. Disconnect the F terminal at the voltage regulator and touch the wire to ground for only a second, while watching the ammeter. The generator should output maximum amperage with the field wire grounded. If it still won't full field, try the same test directly on the generator -- if it full fields now, repair the field wire to the regulator -- if it doesn't full field, try polarizing the generator before getting a new on.

The following section talks about polarizing a generator.

The voltage regulator should regulate voltage between 13.5 and 14.5 volts once the engine has been running for a few minutes. If voltage is too high or low, but the generator full fields, the voltage regulator is probably bad. Before purchasing a new regulator, make sure it's the correct one for the motorcycle. In addition, also try polarizing the generator. Pay attention to the regulator's working voltage -- 6 or 12 volts depending upon application.

Martin doesn't mention adjusting the airgap on the regulator, but I seem to recall there being a shop dope article in the Panhead Service manual. The one I have is '48 to '57, but it should be applicable to your '58.

Post Tue Mar 10, 2020 1:52 pm

Posts: 50
Location: Santa Fe,NM
I disconnect both wires from the generator, connect voltmeter positive to A terminal, negative to ground, start and rev to over 2k rpm, touch F terminal to ground momentarily and voltmeter should read at least 12.5 volts

Post Mon Aug 30, 2021 3:55 am

Posts: 1
Hey George, RooDog here....
If you leave the F grounded more than momentarily the genny will run wild with all kinds of voltage. I only tried this once and 24 volts was seen. The vibrating points inside the regulator is what maintains a somewhat steady 13 v output, or whatever they are adjusted to....

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