Amazing condition given the age of the bike. Merziac and others are correct , I would use gentle , non detergent soap to clean. When I had a classic car I always washed it with baby shampoo. It cleans with no damage to sensitive paint . Just a few drops and Luke warm damp wash cloth. There are a lot of products that are on the market for preserving the finish on older paint, although the paint on that bike looks very nice . Probably one of the easiest restorations I’ve seen here because it looks so good already.