Success! (In a round about sort of way).
So I was using the coil ripped out of an old 24 volt relay as an induction coil for the CDI trigger by passing a magnet passed the induction coil and inducing the desired spike (emf) which the SCR is looking for to trigger, and of course worked like a charm. Good sparks.
Yes I too suspected that at least for my CDI unit, I needed a high pulse voltage, more in line with what the induction coil would be emitting.
Then I thought, well what would happen if I used a simple hall circuit, via the cathode of the BC558 transistor to send a pulse to the external induction coil while the coil was still connected to ground and the trigger of the CDI? The coil would be energize and on release of the voltage spike. Well it worked! Then I tested the unit on the lathe at 2,000 rpm with a 9 slot interrupter.... 18,000 sparks per minute using the Hall sensor as a trigger. No problem and with a 5 mm plug gap!
I then replaced the rather bulky 24 volt induction relay coil with the coil from a very small 12 volt reed relay. It still worked and at 18,000 rpm.
Oh and using a timing strobe light I noticed the unit has a crude advance / retard. At below about 700 rpm the unit is fully retarded any rpm above 700 the unit jumps to about 25 degrees advance, there is no apparent curve , just advance on or advance off . I would suspect this is to aid safe kick starting on a bike or quad bike.
I can use this!!!