Interpol 2 retard boxes .
This little black or grey box can be found under the seat held down by a clip , bolted to the rear ‘mudguard’. It’s full of integrated circuits and variable resistors and is connected in line between the ignition trigger and the electronic ignition box. The retard box is designed to provide an even tickover , it senses engine speed and below 2100 rpm introduces a delay thus retarding the ignition ( as much as 50 degrees! ) . Unfortunately , the container Norton chose to use for this device is not always waterproof and when this box fails , it effectively severs the link between trigger and ignition box so the bike stops , often with a few loud pops and bangs.
Though it means losing that nice even tickover I often wire the retard box out completely , its one less unit to give trouble , idle speed can still be set to 1200 rpm ish and pickup from low speeds is no longer hampered by too much retard.
What to do:
Remove the retard box,completely disconnecting all the wires as you go.If the positive supply to the retard unit (red) has a piggy back connector , be sure to reconnect the other wire it connects with, or the bike will not run .
With the retard box removed you will have two wires coming from the left side of the engine , usually grey and grey with black these are ignition trigger wires .
Connect the ignition trigger wires with individual bullet connectors to the two wires of the same colour on the electronic ignition box .
One note , the output from the retard box (purple ) connects both left and right sides of the electronic ignition box together , do not leave these two wires connected to each other , it cannot work- the ac output from the ignition trigger would be cancelled out.
The blue wire can be ignored, it connects to a heat sensitive switch which goes to earth.
With a little thought you can use the info to reconnect one –but don’t expect it to last for ever.
Graham Wilshaw.