coil question on my 80 gs850 gt

[mottacycle]

Sorry I'm not the best with electrical but how do I check supplied voltage from coil to batt also ordering a new set of caps

[Dogma]

There is a plug from the wiring harness to each coil. Unplug it and check the voltage across the two pins in the plug with everything on. You want that to be as near as possible to the voltage across the battery's terminals (roughly 12.7 Volts for a charged battery). I've heard a GS will run with as little as 9V to the coils, but not well, and on the verge of leaving you stranded. The lower voltage would be due to dirty and corroded contacts in all the plugs and switches between the battery and the coils. The same dirt and corrosion is what causes the charging system to eventually eat itself if not dealt with.