I dived in and did the startus mod to my 8v GRiSO 1200 today.
New cable and fuse from Bat +ve to start relay yellow input.
Insulated original cut yellow with a red splice and some heat shrink.
re assembled... and... click.
Much head scratching later , and Ive cleaned up the main earth point above the starter,
removed the starter motor and checked the brushes and cleaned the commutator.
re assembled ,... and... click..
More head scratching and removal of the starter motor (bosch) revealed that the brush holder plate on
uses bent "tangs" to earth out to the chassis.
These were re positioned so that they actually made some meaning full contact, re assembled everything and....
It looks like the fault may have been the brush plate in the first place