Three four-axle diesel railcars were delivered in 1942 from the Hungarian manufacturer "Ganz" for servicing passenger traffic on the line Septemvri - Yakoruda. They were complemented by three trailers of the same type. The delivery was negotiated on December 9, 1939, but it was carried out in August 1941 and the railcars were prepared for trials later the same year. Due to necessary adjustments of the track between Septemvri and Velingrad, they were put to operation on August 10, 1942 and assigned the series 81-00. They consist of three attached cars, each equipped with six passenger seats second class in a separate compartment and 35 third class wooden seats in a common saloon. The two passenger compartments are separated by a technical and luggage compartment, a restroom and a heating room. Unfortunately, no pictures of the series 81-00 are available, but the railcars' exterior is identical to that of the 82-00 series, pictures of which are to be found below.
            Railcars of the series 81-00 were used for 25 years. There is not a single unit of them preserved to this day.