..if someone here can get 1 good idea from the pics...
like Pat said, vmb... they seem to run springers a lot.. or ran many different styles than we are used to, in the past.
That UK site led me to looking at the Garelli Mosquito on youtube, I think they call it a 38A motor... neat little motor and friction drive setup! Then I found one where a guy was heating up a plate on the side of the cyl head with a propane torch... for a minute or so, it seemed! maybe it was a diesel???
All the dialogue was Deutsch, and maybe the vid was from Holland?
anyhow, it said Lohrmann Fahrrad Hilfsmotor.
None of the ones I saw were power-house screamers or even fast at all... but I don't spend much time watching the 'tuning' vids, as they call it.
That LFH motorbike had a really interesting springer on it... a girder, but the mounts were positioned differently than we are accustomed to seeing on the Indian type springers.
Best
rc