This would give a harmonic balancing effect similar to a balancing shaft would it not?
Trainees on the training course I attended in 1969 were tasked with stripping one of these engines and then explaining how it worked, the instructors must have had a laugh at some of the hilarious answers, including mine I suspect!
In those days a lot of small plant was starting to have Japanese engines fitted, we were not trained at all on these as the ex REME instructors wouldn't even talk about them, let alone ever allow one on the premises!
Wow! What a name from the past, he used to write very enjoyable articles in one of the Bike mags in the early 70s, I really admired his enthusiasm for his subject and his ability to infect his readers with it, top man!