Ironhead Alternator Swap
(text and pictures by Mark Trotta)
If you're having charging problems with your Ironhead Sportster, the least expensive solution is a generator to alternator swap. As an added bonus, your bike will lose several pounds of weight in the conversion.
The V-Twin #32-1673 alternator conversion kit gives you a black alternator and a black voltage regulator.
For a few dollars more, they can be had in chrome, V-Twin part #32-1674.
Generator to Alternator Conversion Kit
The kit is designed to replace the stock generator on 1957 to early 1984 Sportsters. It will also fit 1941 through 1969 Harley FL models.
NOTE: If it is to be used on older, pre-1965 Harleys, the generator bolt holes in the engine case may need to be drilled out to 5/16".
Included in the kit is an alternator, voltage regulator, mounting gasket, bolts, washers (if needed) and instruction sheet.
The alternator itself is compact, about 3-1/4" long, and weighs half as much as the original generator. It has a rating of 17 amps at 1000 rpm.
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Installation
I've installed two of these alternator conversion kits (1976 and 1981 Sportsters). The procedure is straightforward and requires no special tools, except possibly a gear puller.
First, remove the old generator and remove the gear from it. Sometimes the gear is stubborn and you'll need a gear puller.
Next, install the old gear on the new alternator. After mounting the gear it gets secured with the supplied 5/16" lock nut.
NOTE: If the splined part of the alternator shaft is still seen after the nut is on the gear, you'll need to remove the nut and install a 5/16" flat washer underneath it.
The alternator mounts to a stock XL cam cover with two 5/16" bolts.
If you're missing the mounting gasket (OEM 30143-58) you can buy one here.
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Voltage Regulator Installation
The voltage regulator can be mounted in several spots. On the 1981 Sportster pictured below, it was mounted in the stock location, on the front frame down-tubes.
On earlier models, it can be mounted behind the battery on the left. For this, you may need to run two wires up to the alternator it they're not there already.
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Voltage Regulator Wiring
There are three wires coming out of the voltage regulator.
The two shorter wires go to the alternator.
The long wire goes directly to the battery.
Be sure the voltage regulator is well-grounded (a clean, paint-free surface).
NOTE: After the bike has been running for awhile, check the two mounting bolts and re-tighten if needed.
Problems with Generator to Alternator Conversion
The voltage regulator that comes with the alternator conversion kit is foreign-made. On my old 1976 Sportster, the alternator stopped charging the battery, but after diagnosing, turned out it was the regulator that was at fault.
So, if you install an alternator conversion kit and experience charging problems, you may want to replace it with a better quality regulator.
If a clunking noise is heard once installed and running, stop the bike, remove the alternator, and re-tighten the gear. Make sure that the splines are not extending past the gear. If so, add the supplied washer.
Another negative about this system is that there is no simple way to keep the indicator light. If anyone knows how to, please email me and I'll add it to this article.
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Conclusion
A generator/alternator swap is cheaper than having the generator rebuilt or installing a Cycle Electric generator. On a 50 year-old Harley, it should really be considered a performance upgrade.
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