So I had a go at it last night - found the connector behind the ABS ECU in the right fairing panel, shorted out the top two wires and ran the tests.
Test 1 - make sure kill switch is off so the bike can't start, battery needs to be well charged so best to put on a charger/tender.
Turn on ignition and hold down start button for 5 seconds or more. Let go and then brake with both front and rear at the same time and hold.
ABS motor fires up and pulses the front and then rear in turn for a few cycles. Lever and pedal should 'pulse' as the systems pumps.
Test 2 - Kill switch off etc as above, but this time hold the brakes on with ignition off. Then keeping the brakes fully on, turn the ignition and keep holding. The pump will again go through it's cycles.
The tests worked fine and the motor ran, but the 'pulsing' wasn't what I was expecting and it felt more like just a vibration and quite weak, so I'm thinking years of never operating has left the ABS pump full of older and older brake fluid gunging everything up, and it's not really releasing pressure as it should.
The problem is, when actuated, it doesn't move the fluid much, as the bypass that releases the pressure on the brakes is just a bypass section and as it's all a sealed system, the fluid can't really travel anywhere, just releases the pressure on the system.
So my thinking is, if I run the tests and then bleed the caliper as the pump is pulsing, it should (by my logic) push fresh fluid into the pump as it opens/closes the solenoid. Might allow the old rubbish to clear and then the new clear out any blockage/debris and get it working again.
Who knows, will try and see. At the worst the system is simply a non-ABS bike, which I've ridden for decades anyway, so I'm not too concerned about that, just be nice to get the system working if I can.