I found this interesting but somewhat sad story about the race development of a 2 cylinder Puch racer made by marrying two single M125 engines.
I thought I would share the English version.
The attempt by the Graz engineer Albin Sterbenz and the very talented mechanic and racing driver Alois Hofer, to design a competitive twin-cylinder racing bike in order to later on build a good production model from it, deserves its own chapter in the Puch racing sport history. Unfortunately this chapter is also the saddest one, because it marked not only the end of the company’s engagement in racing, but racing also claimed the life of Alois Hofer, born 1933.
One could tell a lot more, but here is just a brief summary: The twin-cylinder engine consisted of 125M engines. Experts know, but a brief reminder, we are talking about single-cylinder engines. After a lot of work they finally obtained 50 PS in the performance test, a tremendous result at that time.
Since such an engine had never before been put into action, it required of course an appropriate frame. It was a tubular frame patterned after the Norton Featherbed frame. For the transmission a 6-gear dog clutch unit was used since the bike was primarily raced in the mountains.
For the engine number the birth date of Alois Hofer was chosen: 28633, i.e. June 28, 1933.