Hey Sam.....I met the owner of Ace a couple years ago, he is a friend of a friend. He had a CB750 at the time and he knows these bikes well.
Your 500 looks super clean, how'd you find it?
These old Hondas are nearly bulletproof and will run forever with just a minimal of maintenance. The single most important item needed for a good running SOHC are clean carbs. If gas has been in them for a long period it can clog the jets.
Along with that is a clean fuel supply. If unsure how old the fuel in the tank is, may be a good idea to drain it and clean the petcock.
Honda recommended a tune up every 3000 miles, this may be a good idea to do as well. Search for the details on it.
You need an air filter?
http://www.amazon.com/Honda-CB500-Air-filter-OEM/dp/B007N8TFDK
Damn, Stev-o....that was quick. I found a few overseas and the shipping and exchange rates were looking a bit silly. Spent too much time on ebay after the searched and didn't consider amazon.
I found that bike in Michigan after a purchase on ebay fell through....the guy ended the auction after I gave him his offer price...go figure. The gent in MI has supposedly owned it for quite some time....bought it from the first owner which was a neighbor. Like most things, I won't know what I got until I get it. Shipping will take a few weeks at min.
I figure I'll do exactly as you suggest and drain all fuel and do a fuel system inspection. I'm hopeful it hasn't all gone to gunk. See what kind of shape the carbs are in...I hate tuning stuff. Do you simply run whatever fuel's available in yours? I know I don't want anything with much ethanol in it if it'll sit....attracts too much moisture.
Oil and filter change. Probably use Rotella diesel 10W40....stick to a conventional given the wet clutch. Shout out if you prefer something else down here.
I'll check the ignition and see if it's good enough to start. I'll likely replace the points, cables and plugs as need be.
Brakes next....drain fluid, replace with some DOT 3 and bleed the system...see what's what.
I'll check the air filter...figure it's due for a change.
Tires and tubes look like they're due for a change.
Will be interesting to see what the block sounds like. The lower mufflers are rusted out. I'm getting two new ones with the purchase but I'm not sure which of the four I'm getting. Exhaust change will come at some point.
Sam