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Tech tip on 12-Volt Conversion

Here's one for the guys still riding the older Iron, specifically older XL'S, Knuckles, Flatheads, Panheads or swap meet specials that are running 6-volt charging systems.

If you're starting to have trouble seeing at night or are worried about getting run over (because that 6-volt bulb lighting up your tombstone can't been seen from more than 6 feet away) Maybe you ought to give some though to swapping over to 12-Volts. I changed both my Pan and Servi-car to 12-volts a couple years ago, and the difference is unbelievable. I'm still wondering why I waited twenty some years to do it.

On top of the obvious benefits of brighter lighting, there is also the facts that your bike will start easier and 12-volt batteries will be much easier to find. Interstate quit making the old H-2 a couple years ago, so if you still run that tall square battery you usually end up with some Taiwan piece of shit. While a 6-volt 2-brush generator will usually keep some resemblance of a charge in your battery, If you have a 6-volt 3-brush, you are probably use to shutting off the lights and trying to make it home in the dark with no lights before the battery goes dead and the 'son of a bitch' just up and dies in the middle of nowhere..

So if you are ready to go to the 12-volts, but are afraid of the cost or work involved, cheer up! It's not that bad....You will have to change the battery, all the light bulbs, generator, coil, regulator and do some minor wiring to complete the job...The 65A 12-Volt 2-brush generator will bolt right in anywhere a 6-Volt came out of.

On all Knuckleheads, most Flatheads and Pre-1958 XL's and Panheads, you will have to drill the mounting holes in the cover and cases out to 5/16". The old gear usually can be made to work, but there are some exceptions, especially on Sportsters.

If you have any doubts, pull the cover and check the mesh. You can change the horn at the same time if you want to, but a 6-Volt horn won't die immediately from an occasional 12-Volt jolt.

If your down on your bucks, instead of paying for a new horn, you can go to the junkyard and get one from a junk car for a lot less. Old GM horns are pretty much the same as the older Harley horns. You'll have to do some fabrication to get the Harley chrome cover to fit, but other than that, it will work fine. The only drawback to converting to 12-Volt is if you are using a stock type 36-64 horseshoe oil tank. This type of oil tank was built with an H-2, 6-Volt battery in mind. The only 12-Volt battery that fits this oil tank is a 12N5.5-3B battery. While the length and the width are fine, this battery is a lot shorter than the 6-Volt it replaces. It is also kind of shy in the amp-hour department. Expect to go through these batteries a lot. (You will)

If you want to do it right, V-Twin makes a battery extension box (part#42-9916) that really works great and will even let you use the stock cover. The battery needs to be checked for a water a lot. In fact a lot more than most bikes, because it is really too small for the job and is constantly being overcharged. There is a solution for this also.. Cycle Electric makes generators and regulators for Harley-Davidson. They make a special regulator just for this horseshoe oil tank/small battery 12-Volt conversion. They have lowered the charging rate just slightly enough to keep the battery from cooking.. Actually they make this regulator in two different styles. They make one type that resembles an Accel electric type or late model (70 up factory regulator) They also make one that bolts to the end of the generator. This type resembles the old "Electric Franks" units...This regulator (V-Twin #32-9282) really works. It comes with a one year warranty. They also make a combination generator/regulator unit in standard or the reduced output version. One drawback however, it won't clear the clutch pedal bracket on a 45 Flathead. The generator by itself is about $200.00. Add another hundred and you can get the combo. Cycle Electric will warrant generators and regulators for 1 year, but if you buy the generator with the built-in regulator they will cover the whole unit for 2 years. ..They will even Red-Label you a loaner if your stuck on the road somewhere during the warranty period.

Would you like to order any of these parts now? 
All parts can be ordered at left..

You will also find these in the Harley Index

generator with built-in regulator 2-brush generator mechanical regulator
Generator with built-in regulator 2-Brush Generator Mechanical regulator
regulator, generato end cover battery box extension
Regulator, Generator 
end cover type
Battery Box Extension

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Tech Tips written by Gary Rask