tech11

Most all of you have run into 30+ year old Brit bike wiring harnesses
that are falling apart, have broken wires, and bad end fittings. And
most all of you have had problems with rectifier modules, Zeners,
Lucas capacitors, condensers, points, mechanical advance mechanisms,
bad switches, bad coils, bad grounds, and Lucas ET system components.
You don’t have to suffer these ills if you are willing to give up the
originality of your Brit bike. Most of the bikes I have built are dual
sport bikes, either used directly as dual sport bikes or converted to
be used strictly on the street. On every one and several of my friends
bikes I have chosen to throw away the stock wiring and start over. In
the process I have also thrown away the Lucas ET system components,
Lucas rectifiers, zener diodes, Lucas capacitors, points and
condensers, mechanical advance mechanisms, and lighting switches.
Original my bikes are not but the electrical systems are modern and
connected with new quality wiring with correctly installed new end
fittings. Most of you would not know where to start to replace those
components and the associated wiring so I’ll attempt to enlighten you.

I have talked here in the past about modern electrical components that
are used to replace the crummy Brit stuff. I have recommended the
following items and here is a little review. For the ignition system
the points, condenser, and mechanical advance system is replaced by a
Boyer Analog Electronic Ignition system. At the same time the
troublesome old Lucas coils get replaced by either two 6 volt coils or
the double spark plug output “dual” coil for twins or a new 12 volt
coil for singles. The “power” part of the system, the rectifier and
zener, is replaced with either a Tympanium for a battery bike or a
Boyer Power Box for a battery less system. A slight modification to
those recommendation is to use the Boyer Power Box with a 2.2 Amp-Hour
“computer” Gel cell to minimize the size of a street application where
lights are used regularly, and still have the option of perfect
battery less operation if the battery fails.

To simplify the wiring I use two toggle switches readily available
from Radio Shack: A master ON/OFF-single pole, single throw, 10 amp
rated and a lighting switch-double pole, double throw with center off,
10 amp rated. The master ON/OFF switch turns off the bike completely.
The lighting switch is wired so that the center position is all lights
off, left is high beam on, right is low beam on, and either high or
low beam on makes the tail light be on. The brake light is on when
ever the master ON/OFF switch is ON and the rear brake lever is
depressed. The master ON/OFF switch is mounted in a hidden place while
the lighting switch can be mounted on a very small plate supported by
the handle bar mount front two bolts. The existing switches, if there
are any, can just be wired around and left there for originality
(obviously I just throw them away as originality is really not in my
vocabulary). As an aside Keith Moore has literally dozens of those
neat chrome headlight assemblies that take 5 3/4 inch auto or
motorcycle sealed beam lamps. They are new old stock after market and
can be fit to almost anything and not look out of place. See Keith’s
ad in the PA for his number.

For wiring I use good quality auto wire bought in 100 foot spools of
various meaningful colors, all 16 gauge. The end fittings are good
quality crimp style (soldering can be used if you have any doubt about
your ability to crimp well but aerospace uses crimped end fitting for
everything including space projects). Every component in my systems
can be removed from the bike for repair or replacement without cutting
any wires. This is possible where lugs are part of the wiring
connections to studded devices or through the use of push together
male/female plugs. The “bullets”, I have found, are not secure enough
so I use the spaded style male/female plugs that are available in
several widths with the smaller variety (sub 1/4 inch, I believe) my
first choice. I use both shrink tubing and slit corrugated tubing to
make the installation look neater along with tons of tie wraps.

For the most part my systems are dead simple but the tricky part is
the lighting switch. It has two poles (two separate circuits with the
lever mechanically connected to both). The 12 volt master ON/OFF
switched power is brought to it. The switched power goes to the center
terminal of both poles. One pole routes the 12 volts to either the
high beam or the low beam elements since those lamps are connected to
each end of the switch on the same pole, selected by either left or
right lever positions. The other pole is wired so that the tail lamp
gets switched 12 volts in either left or right lever choices since the
tail lamp wire is connected to both terminals on the ends of the
switch’s other pole.

The most important part of a electrical system is the grounds. Ground
is a term used in vehicle electrical systems. It means that the
conductive metal chassis is used instead a return wire. While that is
ideally good, the fact is that rust and other corrosion reduce the
conduction quality of that path as to be only poor in many systems.
This problem can be avoided if a common point ground is provided for
all components in the system. It requires a well grounded stud with a
freshly removed paint bonding point on the frame. A return wire is
carried to this point for each of the following parts of the system:
the headlight shell, the tail light assembly, the rectifier/regulator
electronic module, the electronic ignition module and the battery (if
used). The conductivity of the motor to this point should be verified
and enhanced with a jumper wire if deem necessary because the spark
plugs must use the motor and frame as part of the return path.

I find it most useful to use a studded terminal as a switched 12 volt
distribution point. I wire the output of the master ON/OFF switch,
termed switched 12 volts, to the coil and use the coil’s terminal as a
common distribution point for each circuit requiring switched 12
volts: lighting switch, brake light switch, and the Boyer Ignition
module. If the system includes a battery it gets 12 volts from the
Boyer Power Box or Tympanium directly, but through a fuse of about 15
amps. This means that the rectifier/regulator is always connected to
the battery but internal diode action in the electronic module keeps
the battery from loosing its’ charge through that path.

Finally there is the issue of positive or negative ground. As stated
earlier the “ground’ is just a conductive path to complete the
circuits. Whether the system is wired positive or negative ground does
not impact it in the least but every component in the system must be
connected to ground consistent with that choice. I find, being
educated in the USA, that it makes more sense to me (read as “familiar
to me”) for the system to be wired negative ground. The only departure
I have to that is one bike where I retained the original rectifier and
zener. Those original components are made physically to be connected
positive ground so that dictated the system to be positive ground.
Modern electronic components like Tympaniums and Boyers can be
connected into a system that is negative or positive ground as long as
the whole system is so wired.

I hope this helps in redoing your electrical system and remember to be
neat and to record your final system with a neatly done schematic
drawing or wiring diagram.