One solution we have found for an alarm for a Honda CB500.

1.Power Supply--- Connect the positive and negative supply wires of the alarm system direct to the battery terminals.

2. Engine immobilisation---Cut the yellow wire of the white 4 way connector that is available inside the rubber protection boot behind the right fairing, near the starter solenoid.

WHAT!!! The CB500 has never had a start soleniod behind a fairing ( like every other Honda motorcycle produced ). More to the point the CB500 does not even have a fairing!! ( see pic below ) The CB500 does not have a yellow wire on any ignition related 4 way connector ( or even a yellow wire at all from any 4 way connector -- See the CB500 wire diagram attached).

I would like to help my fellow bikers from any potential problems but I have been asked to remove the sellers id.

However its worth noting that an new ECU for any bike is about £400 and so having the correct info is vital.