Quick update here. I have had the Lucas LRS 100 starter motor tested (along with the same model from my next 7 project) and both pronounced to be in fine health. I re-checked and recleaned all the connections. Tried both starter motors to no real success. I then had the battery tested (2021 one from Halfords) which easily exceeded the rated CCA and was pronounced in fine health. Then I experimented with reducing the ignition advance by rotating the dizzy. It was too advanced and I had a bit more success. It would successfuly crank about 1 time in 5, better than nothing. But with nothing else left to try, I have bitten the bullet and ordered a new hitorque starter motor, The starter motor man at Burghfield (who is excellent I have to say) assures me that being a pre-engaged type, the run in on the starter motor teeth will do the job just fine without having to do any ring-gear changing. All 4 race cars I have with ford engines happily run pre-engaged starter motors without changes to the ring gear, so here's hoping that a/ it'll be ok and b/ solve the cranking problem. Hopefully find time to pop it on over the weekend and even more hopefully give the final update! Anyone want a Lucas LRS 100 starter motor tested by the starter motor man?