On the Dunstall GT750 project, we decided to fit a set of nice period looking small LED indicators with a suitable electronic flasher relay.  They looked fantastic, but like many bikes of that era, the dashboard warning light a.k.a. the idiot light is wired across both sides so that one bulb flashes for both sides.

That's a great way to keep things simple but with LED flashers all 4 usually come on at once.  I suppose I could have tried an LED idiot bulb to see if that would work, but why do something simple when you can try something more elegant.....
 

Diodes are sold commercially on a band. They are banded for use in automated circuit manufacturing facilities.  They are are also available singly from on line stores and some Radio Shack stores.

These are relatively high voltage diodes that are used in our Motoplat and PVL kill switch wiring harness and are somewhat of an overkill in this application, but that's what was available, and the stores had closed and I needed to tick off another job on the list.

The first step was to remove the idiot light sub harness and carefully extract the appropriate pair of connectors from the connection block.

With this set, all connectors were removed for cleaning and to make it easier to see.

Next, I had to cut both leads to the bulb to splice in a pair of diodes.  In an OEM set up, one bulb is wired in between the left and right circuits, but with LED indicator bulbs, that allows voltage to bleed from one side to the other and all 4 flashers will probably flash if you select Left or Right and that's not a lot of use.  Diodes are basically a one way electron valve.  They allow power to flow in one direction and not in the opposite direction.

As you can see from the diagram and photo, I turned the diodes around so that they are less likely to be broken if the harness flexes at all.

Before you solder it up, check that it works and if it doesn't, try reversing the diodes.

Apply heat shrink tube and/or electrical taps and reinsert the connectors into the connector block.  You will also now have one additional lead which goes to ground (earth).

Refit the sub harness, ground the ground lead and with any luck the flashers will work like and charm and so will the idiot light.