2 Brush or 3 Brush Generator

[Jimmy]

I have a 59 FL with a 6 volt system. Can I tell if I have a 3 brush or 2 brush generator without removing it from the bike? I read on another forum that you should not use a sealed battery with a 3 brush generator that it might explode from overcharging. Bunk or not?

[Jimmy]

Ok, if all else fails read the dam manual lol. The first paragraph in my service manual says "The standard generator is a direct current two-pole, two brush unit with the charging rate governed entirely by a voltage regulator. So I assume I got a 2 brush unit. I'm really a dumbass when it comes to electric but I'm trying, you know the old saying about old dogs lol

[Rubone]

Jimmy,
Yes, the standard generator is 2 brush. You can easily tell by what type of voltage regulator it has . A two brush regulator is about 2 1/2 inches square, a three brush relay is a small rectangle. The generator also has two nuts on the end of the body by the left footboard.
And sorry to spoil your fun, but ANY battery has the potential to explode in overcharge conditions. A lead acid battery produces hydrogen gas as a natural function of its charging. When excessively charged they can boil and expel large amounts of gas which is both corrosive and highly flammable. Does it ever happen? extremely rarely. Will a gel battery explode? Again, extremely rarely.
If handled correctly and with charging systems kept in good order they are fine. Don't worry about it.
Two brush systems became standard in '58.
Robbie