What is this engine (continued)

[fatfreddy]

re:

here are the photos:







I will make other photos at your request if necessary, thank you
beforehand

[elephant]

??

There is a fable where blindfolded scientists must recognize an elephant by being able to touch only its trunk .....

[rico22290]

mmh, a bike engine?
The error is possible, thank you.

[Christophe]

Double subject, please copy / paste your answers here: https://www.econologie.com/forums/c-est-quoi ... t8902.html

I lock this one.