AFAIK, most non-estart British bikes with 12 volts batteries came with 12N9 (Lucas PUZ5A) or 12N7 batteries. CCA can vary for different amp/hour batteries and CCA is not very useful a number for non-estart bikes. 12N9 describes the voltage, physical size, that they are 9 amp/hours and 12N7 is smaller and 7 amp/hours.
IMHO, either works fine with any Lucas rotor/stator and with the original charging system or any of the modern replacements. Unless you're adding lots a accessories or bulbs that require more power, the original 120-watt stator is enough. If you ride at low RPMs for long periods, a 3-phase stator might make sense but otherwise anything other than the standard stator is a waste of money and there is no use for the extra current they provide. Also, 7 amp/hours is more than enough unless you plan to run your lights or accessories with the engine not running. Finally, even the 14 amp/hour batteries that barely fit the battery carrier will work with the original charging system, but they are a real waste of money in most cases.
I generally use 12N9-4B-1 (12N9 with the positive terminal on the right). BTW, PS-YB9L-B is basically the same as 12N9-4B-1 but a different numbering system.
