Sweetpea is correct, GS1100E (although missing the side covers and with one of the FUGLIEST paint jobs I've ever seen.)
Actually the valve train is pretty simple. None of that fancy shim & bucket stuff.
However, I have no idea how expensive it would be to have the head overhauled, but I don't think it's beyond the skills of the average SOHC owner if you wanted to DIY.
In our neck of the woods they go for between $800 and $2000 depending on condition. Although, since Suzuki only made that particular model for about 3 years they are rare-ish.
It's a fantastic bike. More torque than you could ever need and a bottom end that is built like a bank vault. Great compliment of gauges, too: oil temp, fuel, gear position, idiot lights for headlight & tail light out, self-cancelling blinkers, etc...
It really was Suzuki's top of the line model in the early eighties.
For $100, you could do a lot worse.....
-JP