Posted by: Mike Clark
Found some pictures of the thing now - could be it.
I donít think it is a steam motorcycle - not enough space for steam generator and in any case you wouldnít need such a small wheel with steam torque.
Iím no expert on motorbikes but remebered a picture of a very odd motorcycle which had a pair of horizontally opposed cylinders with no normal connecting rods, just a strut between the pistons which had a central gudgeon pin sliding in a pair of slots (steam engine crosshead fashion) and took the little end of a long connecting rod straight to the back spindle. No clutch and no gears, just scoot to go. If I am right that is why the back wheel is so small. It was called the Hildebrande and Wolfmuller Motorad. Couple of images here which look similar but not identical to our picture.