Servi-Car Electrical Upgrades
Article by Mark Trotta
Harley Servi-cars are old, slow, and heavy. There's very little we can do about the slow and heavy parts, but we can make them a bit more modern.
The trike featured in this article is my 1961 G Model, which I have been restoring on and off for several years. Electrical upgrades included a 6 to 12 volt conversion, AGM battery, and Cycle-Electric generator.
12-Volt Conversion
All pre-1964 Servi's had a 6-volt electrical system. If you decide to convert to 12 volts you'll need to replace the battery, and the original battery box is small and odd-shaped. But inside the cargo box there's plenty of room (more about battery below).
Wiring Harness
When in good condition, 6-volt wiring and switches are more than enough to handle 12 volts. But considering that most are now 60+ years old, chances are the wires are cracked and frayed.
If you have the old harness, it's not too difficult to make a replacement harness yourself. Black cloth looms are readily available in 1/8", 1/4", 3/8", 1/2", 3/4", and 1" sizes.
Read: Wiring A Motorcycle From Scratch
Points, Condenser, and Coil
Ignition points will work with either 6-volts or 12-volts, but condensers are different and should be replaced.
When converting to 12 volts, you should upgrade the ignition coil. A 12 volt coil has more windings and will work much longer than the old 6 volt coil.
Pictured above is an Andrews 12 volt ignition coil, which fits many 1965-1979 Harley models, but will not fit the original Servi coil bracket.
My solution was to fabricate a small bracket and mount it underneath the seat.
Battery Size Matters
You've likely seen pictures of full-size automotive batteries in Servi boxes. Although this may look like a good idea, it puts a strain on the already marginal generator.
Bigger batteries require more amps to fully recharge, which adds stress to the original charging system. It works the other way as well - too small a battery can't handle the generator's output.
The output of the generator should dictate how big/what amperage the battery should be.
Battery Tray
To help keep with the all-Harley motif, I did a little research and found an Evo Sportster/FX battery tray that 'almost' fit.
With just a little modification, I got the bracket to fit without drilling any holes in my original metal box.
Yuasa YTX20L-BS fits many Harley Big-Twin models 1997 through 2017. It also fits 1997 through 2003 Sportsters. It's rated at 18 amp-hours and has 270 CCA (cold cranking amps).
Dimensions of the YTX20 are 6-7-8" length, 3-7/16" width, and 6-1/8" height.
NOTE: Batteries should always be well secured so they can't move over bumpy roads or hard braking.
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Cycle Electric Generator
The biggest expense of the electrical upgrades was the Cycle Electric DGV-5000 generator with regulator, which is designed for use in pre-1984 Harleys with a 7-amp (or larger) battery.
Featuring a built-in regulator, the C-E unit provides higher output and longer service life than a stock unit. There are several styles of oil deflectors and you will need to re-use your old one.
Generator Wiring
It's a simple two-wire hookup. The larger wire goes to the ignition switch (use a heavy grade wire here). The smaller wire from the A terminal goes to the generator signal light.
After the battery and switch are hooked up, the gen light comes on when you click the key switch to "on". The light should then go out when the bike starts up. If the light stays on after starting, it's telling you the generator is not charging.
NOTE: When you buy a Cycle-Electric generator/regulator, they are polarized from the factory.
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Circuit Breaker/Inline Fuse
You need to protect both the battery and the motorcycle from excessive electrical current. An inline fuse or circuit breaker will act as a weak link and break the circuit, stopping potential disaster of melted wires or worse.
I opted for a 20-amp circuit breaker.
The battery cables were fabricated with 10 gauge AWG wire. Positive goes from battery to circuit breaker, then circuit breaker to terminal board under seat.
TIP: Mount circuit breaker somewhere close to the battery.
AWG wire always has more copper content than SAE-rated wire, and more copper is better. This variation is about 10-20%.
NOTE: Make sure both the battery and the motor are grounded to the frame.
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Final Thoughts
The electrical system was the last part of my 1961 Servi-Car restoration. The 6 to 12 volt conversion, AGM battery, and Cycle-Electric generator all went hand in hand with each other. To me, it was worth the extra time and effort and money to make it as reliable as possible.
All AGM batteries are maintenance-free and will hold a charge much longer than a conventional battery. Now the trike can (and does) sit for months and the battery is still completely charged.
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Related Articles
1961 Servi-Car Restoration
Electrical Wiring For Motorcycles
Basic Motorcycle Wiring
Harley Generator - Repair or Replace?
