If it only runs on the choke, it's likely the pilot jets are gummed up. They are the smallest jet, so they tend to get gummed up first by old gas left sitting in the carbs. Be a good idea to strip down the carbs and give everything a good cleaning. If it's your first time, do them one at a time and take lots of pictures as you do it so you can refer back to them as you build them back up. Stealing the wife's muffin tin works great for keeping parts organized.