Suzukis of this era have a problematic charging system. They have a permanent magnet alternator which shunts excess power to ground. As you might imagine, this can cause the components (reg/rec, stator windings) to become quite hot. There are a number of ways to remedy this, the ultimate one being to use a Compufire series regulator/rectifier, which completely changes the way that the excess power is dealt with. This is not a cheap option for a $200 bike, but it has been shown to drop oil temperature in a GS1100 motor by 30 degrees (the stator on that machine is internal and oil cooled). At least that's what Posplayer on the GS Resources website has measured on his own machine. Failing that, the stock reg/rec can be replaced with a Honda 5 wire job from a 450 Nighthawk (amongst others) that is far more robust than the original unit. This assumes that the alternator on the 450 is a three phase, I do not know for sure about that.
There are also many thousands of 80's Suzukis that have never had an issue. Cleanliness of the connectors and proper grounding of the reg/rec makes a huge difference.
