I just did a similar project. Drain whatever is in the gas tank out. Since it´s been sitting for a long time, probably not filled to the brim, there is most likely some rust on the inside that you can or can´t see. Its a good call to clean the tank even if it looks clean. I found a good way to do it without spending money on a gas tank cleaning/sealing kit. Buy a pack of 100 quarter inch nuts from home depot ($1.99) and put them inside your gas tank along with a little bit of gas or WD40 or something to loosen the debris. Shake it rigorously for 10 minutes or until you think all the rust has been knocked of. The nuts act like a wire brush to the inside of the tank (be sure to get all surfaces by flipping it upside down as well. When you think it is good open your gas cap and start shaking the nuts out. This is a project in itself, that last one is always a bugger. When you get them all out you want to flush that tank with water until it is completely clear and all the rust is out of the tank. Then run some gas through it, (alcohol mixes with gas and water so that may work better) but u just want most of the water out of the tank. Then, fill the tank all the way to the top so it does not rust again. You may want to drain it after a day or two to make sure you get all the rust out, but its a great way to clean the tank for cheap and it should only take about 45 minutes. I would drain the brake fluid/pebbles and try cleaning the system out with brake cleaner. Do an oil change and filter change. You will probably want to drain the carbs and clean them while the tanks off because most likely you will have to clean it anyway. These old bikes always seem to be gunked up. I always start with that, then get new plugs, some starting fluid and get her to fire up. Hopefully that helps!