Martyn.
A little trick I have learnt with Lucas magneto's when timing them on your own.
Remove the earth brush and clean out the threads in the body (5/16 BSF on K type), get a 5/16 BSF bolt with about 1" of thread, put a smooth radius on the end and holding the magneto in the advanced position screw the bolt in FINGER TIGHT ONLY. Any tighter and you will risk damaging the armature.
This will lock the armature enough for you to be able to tap the ATD on and start the nut without needing 3 hands.
Do NOT use this to hold the armature while you tighten the nut and remember to remove the bolt and fit the earth brush after.
A little trick I have learnt with Lucas magneto's when timing them on your own.
Remove the earth brush and clean out the threads in the body (5/16 BSF on K type), get a 5/16 BSF bolt with about 1" of thread, put a smooth radius on the end and holding the magneto in the advanced position screw the bolt in FINGER TIGHT ONLY. Any tighter and you will risk damaging the armature.
This will lock the armature enough for you to be able to tap the ATD on and start the nut without needing 3 hands.
Do NOT use this to hold the armature while you tighten the nut and remember to remove the bolt and fit the earth brush after.