I used to overhaul Lucas Starter Motors (among other items) on a commercial basis for many of the other Mini Parts suppliers in Sydney and a few interstate in the 80's and early 90's.
Yes, a good battery is a must with just about any Starter Motor, not just to make it turn over over course, but as they nearly all have a spiral in them to ensure that the Pinion is held hard at the Motor end of that when engaged.
There was one type of Starter used in the Mini (I think it was the 35J ?) that was better then the others. Across the board with the Lucas Starters, I'd find about 1 in 20 had a split pinion, a similar number that had a broken spring, about 1 in 10 had worn the front bush to the point where the Armature had Poled Out on the Field lamination, and the list would go on. I don't ever recall having any that were burnt out though (may have had, but if it was, it would have only been 1 or 2).
Chatting with some of the local Auto Sparks around that time, they all loved the Lucas Starters, it was a great source of revenue for them and they lamented the cessation of production of the British Based Cars as they were just about the only ones who used them. They hardly ever saw Bosch, Nippon Denso, Hitachi that seemed quite prevalent in other car brands. For a short while, Holden also fitted Lucas Electricals over Bosch and Delco Remy, however, that was short lived. I would buy my parts for overhauling these units, direct from Denis Cook at Lucas Service (in Auburn). They also serviced parts there, including other brands. Even Denis often said that the Lucas stuff wasn't great.
I agree that A killer of Starter Motors is weak batteries (as mentioned) and also excessive starting, though you could draw on that 'in one hit' ie, cranking for 30 - 60 seconds over 2 - 3 that would normally start most engines. That all sounds fine, but certainly up to the 90's, Minis probably more than any other car were prone to stopping in the wet and other issues that usually resulted in numerous cranking periods, some longer than other. I'll say here too, from my own experience in overhauling them, that cranking for long periods didn't seem to have any bad effects on the Lucas Starters (though I wouldn't advocate sitting on the key for minutes on end), as by far, the most common issue with them as the Front Bush wearing out, which had next to nothing to do with any heat, but the number of loaded revolutions the motor did. By comparison here, while it is abusive to continually crank on the starter motor, Bosch, Hitachi and Nippon Denso units stand up to that type of abuse time after time without premature wear.
I'm sure some of you guys have seen some photos I've posted in these pages of Mokes going through water bonnet deep. Some of these make it through without stopping and some don't. It's not unknown for the guys that have these Hitachi Starters to continue crossing on the Starter to get high and dry on the other back. The guys with the Lucas units seldom have been able to do this and all that have tried have found they need a new Starter Motor soon after. Those with the Japanese units have never had a need to touch them. Sure, this is quite abusive but it shows how well built the alternatives are and that once fitted will go on for a trouble free life.
When compared to other brands, the Lucas Starters have never been good. That's just not my view, but also that of the wider Mini and Moke community at least here in Australia as the 'Gemini Starter Motor Conversion' is a very very popular one, with many owners not being able to drop the Lucas units fast enough.
I'm sure if you tried a Hitachi or Denso unit, you'd not be too quick to go back to the Lucas Starters.
