OK I got the 'definitive' word from the manufacturer - Centramatic. I went to their website and to the 'contact us' section and posed the question: 1 or 2, if 2 then why and part number. I got answers today (surprising since it is Saturday) from Jerry Robertson, Director of Technical Support. Here is what he said:
GOOD DAY
IT DEPENDS ON IF YOU HAVE ONE OR TWO ROTORS
1 ROTOR ONE BALANCER
2 ROTORS 2 BALANCERS
THESE BALANCERS BOLT TO THE CENTER HUB OF THE RIM ( 5 BOLTS)
HARLEY HAS DIFFERENT STYLES OF ROTORS
IF YOU HAVE THE STYLE OF ROTOR THAT BOLTS TO THE SPOKES OF THE RIM (5 BOLTS)
THEN IT WOULD TAKE ONE BALANCER
SEND A PICTURE OF THE ROTOR TO ME
I sent the photo and his reply was:
YOU NEED THE SET FOR A HARLEY TRIKE WITH 2 FRONT ROTORS MHD 200-201 PART NUMBER
Why 2 when Gary you only have 1? His reply:
2 rotor front balancers have different amount of weight in each balancer, different weight than a single front balancer.
This change to a single front with the open style of rotors not bolt to the center hub is a physical dimensions issue, not for a perform
issue one side of the bike to the other side are not equal dimensions for where the balancer mounts
As manufacturers are want to do perhaps they changed something over the years - product improvement, lower manufacturing costs, who knows, that they recommend 2 balancers with different amount of weight (less I would think) vs just one balancer.
So I'm satisfied that I've exhausted the information available - I know I've exhausted myself, lol, but hopefully uncovered some useful information for all who are interested.
Cheers!