Chain with dimensions 1/2x1/4" with 140 links. The designation is 420 and is the most common chain on Japanese mopeds, but sits on many different ones.
Esjot is a major manufacturer of fantastic sprockets in Germany, but also has equally fantastic chains made in Japan with the same high quality.
They are manufactured under high precision and known to stretch a little and last a long time, better chain is hard to find.
Chain lock included