Found this picture of the Beaulieu tricycle on the net, an other step forward.
Only the head and left crackcase halve is the same as my machine, the barrel is bigger.
The barrel stud is blocked by a pin as Ariel did later in theire aluminium cases.
This is the beginning of proof of it being a cheap B model next the 1900 front engine A model.
Now finding the same quality picture from the otherside.