tech48

Installation of a Boyer Ignition System
by Lynn Bennett

THEORY OF OPERATION:

The Boyer is a transistorized electronic ignition. That is, the points
and condenser are replaced with a simple power transistor used as a
switch. The triggering of the Boyer is done by a set of rotating magnet
that is attached to the shaft that formerly rotated the mechanical
automatic advance mechanism. The trigger coils are mounted on an epoxy
circuit board which is shaped like the former points plate including
slots for fine adjustment of the timing. The Analog Boyer uses the
change in magnetic induction rate from increased RPM pitted against a
fixed voltage comparison to make a variable timing advance based on
engine RPM. The Digital Boyer uses the same trigger coils but varies
the timing based on engine RPM using a small integrated circuit
computer that has several stored and user selectable advance curves.
The Digital Boyer uses an early trigger signal that is delayed
digitally based on a computer computation for engine RPM. The Digital
Boyer uses basically the same transistor switch to control the bikes
coils, but one version uses tuned coils to slightly enhance the quality
of the spark generation.

For batteryless operation only the Analog Boyer is usable, as the
Digital version needs a battery to operate at all. The Digital version
of the Boyer needs to use either resistor plugs or resistor coil wires
or both to minimize the Electro Magnetic Interference (EMI) generated
by the plug firing that effects the computer and makes it skip
instructions and loose its place in its internal program.

For single cylinder bikes the 12-volt Lucas coil can be retained but a
smart installer replaces the Lucas coil with a new PVL coil with a
primary resistance in the range of 3 to 4.5 ohms. For twins there are
two choices: twin PVL 6 volt (!) coils wired in series such that their
summed resistance is in the range of 3 to 4.5 ohms or a single dual
output 12 volt coil whose primary resistance is in the range of 3 to
4.5 ohms.

REMOVAL OF ORIGINAL IGNITION PARTS:

Disconnect the ignition wiring to the coils/condensers and label the
wires with masking tape and an indelible marker. The coils and any
remotely located condensers should be removed from their mounts. The
points wiring should be disconnected at the point’s cavity end and the
point’s plate removed. To remove the ignition cam first remove the hold
down bolt. Then thread the correct bolt into the larger threaded hole
of the cam itself or insert a small piece of round stock that fits the
hole in the ignition cam. A series of taps from a small hammer on the
sides of the bolt or rod at 90-degree intervals around the bolt will
break the taper loose and the automatic advance mechanism will fall
out. An alternative tool is available that is a multi diameter bolt
that forces the cam straight off the taper, kind of like a flywheel
puller.

MECHANICAL INSTALL:

If you choose new PVL coils be sure to buy the appropriate coil
brackets for them. Mount them where they were previously located
modifying the mounting points to assure a secure mount. Beware of
interference with the gas tank. The Boyer Ignition module can be
mounted almost anywhere but close to the coils is ideal.

The magnetic rotor assembly installs into the taper in the points
cavity. There is no key so it must be loosely installed in about the
correct position and tightened later. But first position the engine
crankshaft at the point in its rotation where the plug is suppose to
fire at maximum advance. Later bikes have a pointer in the primary case
and marks on the alternator rotor but verify that the marks are in the
right place. It is possible to install the rotor out of time (forget
the key or ET rotor) or for the alternator rotor to be from a different
bike with different markings.

A gross way is to verify the timing marks is to start by positioning
the engine at TDC. Using a piece of paper make a strip of paper go
completely around the circumference of the rotor, and cut it exactly to
that length. Fold the paper into four segments then subdivide the
segment closest to an end so that you may mark it at the timing point,
understanding that each quarter segment is 90 degrees. Lay the paper
strip on the rotor circumference so that the end is at TDC and the Max
RPM timing mark on the strip is a more anticlockwise direction than
TDC. Make a new mark on the rotor if the original one is wrong.
Double-check your work. Owners of earlier bikes that don’t have the
timing window in the primary cover will have to get the Brit tool made
for these bikes that includes a degree wheel marked in crankshaft
degrees when turned at camshaft speed. The tool includes a timing wheel
mount that bolts to the taper in the point’s cavity. Position the wheel
at TDC after accurately positioning the crank at physical TDC using the
“stop” method and/or a dial gauge in the spark plug hole. Another
option for these people is to update to the later rotor and primary
cover that includes the timing window or to temporarily install a new
style primary cover and mark the original rotor. Some bikes have
crankshaft-locking slots that lock the crank at either TDC or the max
advance firing point. You’ll have to review your specific bike’s
Workshop Manual to determine if you can use this feature.

With the motor at the firing point and holding the new trigger coil
plate up to the points cavity with the plate hold down screw holes
centralized, install the magnetic rotor so that the painted on dot on
the magnetic rotor magnet is visible in the appropriate holes of the
Boyer trigger plate. Triumph twins’ magnetic rotors turn clockwise
while BSA twins’ and singles’ magnetic rotors turn anti-clockwise. With
the two initial alignment holes placed on the bottom of the plate, the
Triumph uses the hole in the plate to the right of the lower coil while
the BSA’s use the hole to the left of the lower trigger coil. If the
magnetic rotor is loosely fit into the taper and the Boyer trigger
plate installed into the points cavity (centered in the slots), you can
reach through the hole in the center of the trigger plate and mover the
rotor until the paint dots is visible through the appropriate alignment
hole. Tighten the rotor hold down bolt to retain the rotor and tighten
the Boyer trigger plate hold down screws. The rotor hold down bolt must
not bottom in the taper. Shorten it if it does. Install a flat washer
and a spring type lock washer under its’ head (not include in the Boyer
kit!).

WIRING:

Someone completely rewiring the bike should make sure the Boyer ground
makes good continuity to the frame, the coil mount, the battery ground
terminal and the engine. The wiring should be done as per the Boyer
instruction sheet, depending on the choice of ground, either positive
(typical as factory delivered) or negative (as on American cars). All
connections should be verified as having good continuity and good
mechanical strength. The trigger wires should be separated from the
rest of the wiring harness as much as possible to avoid false
triggering of the Boyer. In fact, twisting them together also helps.
Maintain the correct connections, especially with the trigger wires.

For using existing harnesses follow the Boyer Instructions. When using
two coils in series be sure to connect one coil’s positive terminal to
the other’s negative terminal with a short wire and then treat the
remain two terminals the same as the originals coil’s positive and
negative terminal.

Good power and ground connections are paramount to a good operating
Boyer. Good continuity for all ground connections (frame to battery, to
engine, to Boyer, to the coil mount) is of the utmost importance.

Unless your bike includes a radio or you are installing a Digital
Boyer, use solid wire for the spark plug high-tension leads, and
non-resistor plugs and caps.

Kill buttons “kill” Boyers if not installed correctly and if they are
not of the correct type.
1). For negative ground system a grounding kill button (connects to
ground when pushed) can be connected to the Boyer black wire that
connects to the coils negative terminal.
2). For positive ground systems the “kill switch” must be of the type
that allows continuity through its connections until the button is
depressed, when that action breaks the continuity. This switch is
placed in series with the supply lead for the Boyer, the white wire.
This connectivity acts as break in the power to the Boyer, stopping the
generation of sparks, whenever the button is pressed. Installation of
the grounding kill switch, as above, on a positive ground system will
destroy the Boyer.

INITIAL TIMING:

The initial timing is handled by the positioning of the magnetic rotor
paint spots in the trigger plate alignment holes. The bike should be
able to run in that setting but by no means should it be operated on
the road without the final stroboscopic timing light adjustment to the
timing.

TIMING LIGHT TIMING:

Start the bike with a friends help. One person controls the throttle
and adjusts the Boyer trigger plate and the other strobes the
alternator timing marks and reports changes. Increase the engine RPM
until the advance of the spark as seen on the alternator rotor stops
and stabilizes. Monitor the alternator marks with reference to the
pointer. Adjust the Boyer trigger plate to get the mark and the pointer
to align at full advance RPM. Secure the Boyer trigger plate screws.
Carefully remove the magnetic rotor hold down bolt and put a drop of
BLUE locktite on the threads. Replace the hold down bolt with its flat
washer and spring type lock washer and tighten it down. Now start the
bike, run up the RPM’s to the full advance point and verify that the
timing is still correct. If not readjust as necessary before the
locktite sets up.

FINISHING UP:

Close the bike all up and forget the ignition forever except for
regular spark plug changes.