BRANSDEN MKIII IGNITION UNITS
the ignition on should produce a steady current through the
ignition coils except for the Norton unit. This remains off
until triggered by turning the engine or disconnecting the
yellow/black or white/black wires.
current through the coils could be caused by:
- No power
to the white wire. (Battery voltage low, less than 8
- No earth
to red wire.
connectors. Tinning gone black or very corroded.
- Coils or
link wire open circuit.
coil wire shorting to earth + (Black box very hot).
connected to black wire shorting inside from primary
winding to case (very common on Norton machines) (black
box very hot).
can rub through to frame, check by removing unit and look around
all the transistor box wires.
battery cells should be in good order as one poor cell will
produce a high resistance supply to the ignition. This can make
the ignition spark on switching lights or horn and in some
cases-may produce a continuous run of sparks.
off ignition should produce a spark at all spark plugs. The
Norton unit would require triggering by turning the engine or
disconnecting yellow/black or white/black wires. (Firing on one
cylinder only, one coil shorting to earth could be either coil).
If test No. 1 is correct but no spark is produced on
switching off, the transistor box is faulty.
transistor box can be tested in circuit by disconnecting the
yellow/black and white/black wires and with the ignition on they
can be touched together and broken, this should produce a spark
at the plugs. If not the box is faulty.