Hello Mark,
I can't answer your question directly, but can offer this (which I found out the very hard way...).
My own TS125 had what I thought to be a good 6v battery - it was showing 6.2v on voltmeter, but bike just would not start. I spent ages messing around with ignition timing, plugs, plug cap etc etc, all with no improvement.
More out of desperation (or inspiration) I bought a brand-new battery. She fired up first kick
I had thought the MZ wouldn't be that sensitive to battery power, but the lesson here I guess is, don't assume a borrowed battery will have enough strength to start the bike.
Rick