Good little motor you have. That thing may very well outlive you if you care for it correctly. Now, you say that it had been sitting in your barn for a while? Also, I assume that it had been sitting for a while before then, as Ga hasn't used that tag in years. That being said, you will want to rebuild the water pump and the carbs. The kits for that should be somewhere around 25 bucks apiece, and are quite simple, provided you have a manual. That being done, you should be good to go, unless you aren't getting a spark. You may have a cracked coil, a bad plug, or a damaged wire or something. Also, your point gaps may need to be reset. If it doesn't need the electrical work, you could do the rest in less than 45 minutes, with basic tools. With the electrical work, you may need another 45 minutes or so, plus possibly some parts.
Post up the model number, and I will be able to tell you the year, so you can get the carb and water pump parts. While you are out there, disconnect the fuel line, unscrew the plug, reattach wire, ground it to the block, pull it over, and see if there is a spark. If there is, you will be good to go otherwise, and if not, I will help you troubleshoot it.