Looks like an '85 ST500 to me, nice bike, I briefly had one, traded off because it was way too big, but it was also all Shimano 600.

I gave $15 for mine, gave it a quick and dirty overhaul, then traded it for my '80 Super Course, had it been 23" instead of 25" I probably would have held on to it, it rode very well, and transferd loads of power.