Alright I looked into this a little further. On the flasher, Br/w appears to be power Black is ground and Br is power from the switch. There seems to be plenty of two prong flashers but the three prong are limited. I can get get adjustable ones for load purposes as the #’s on the OEM case
Those old flashers are load sensitive... more load (watts) and they flash faster.
FN257L
12.8V 85 C/M
27W X 2 + 3.4W
061300.2941
The number before the "C/M" should be how many times per minute it will flash with rated input voltage and the bulb load listed on the flasher.
The 27w is the wattage rating of the bulb in the signal itself (there's two per side of the bike = x2) and the 3.4w is the wattage of little bulb in the indicator in the speedo.
What I’m reading is with a 3 prong flasher, the indicator on the switch is fed from the third prong. If one of your external bulbs burns out, you will notice an immediate change in speed or failure to flash at all. This tells you that you have a problem, however I appear to have the right indicator bulb burnt out but when the flasher was working it didn’t make a difference
With the two prong flasher, the indicator bulb is in parallel with the turning lights and if one of the turning bulbs burns out, you may not notice any change in the flashing rate. Does this mean I can use a two prong?