Does anyone know why the RT3 has two holes drilled in the headlight bucket? The first one is for the High Beam but not sure what the second one is for.
I expect Yamaha used the same bucket for many models.

My guess is the speed warning lamp that became mandated in Japan about that time.  I don't know if any other countries got it?  

"My guess is the speed warning lamp that became mandated in Japan about that time."

Yes, I agree with Mark.

A handful of Japanese Domestic Market (JDM) bikes were brought back to the US by returning servicemen and, as they got sold on to new owners, that red light caused lots of confusion!

Just out of interest, I bought a set of JDM TX500 clocks which have that red light in the centre of the bracket and, when I get the time, I want to sort the wiring out then spin the speedo up with a drill, to see if the light still works. As well as the red light, there is also a red line on the speedo at 80kph.