Bonjour Raphael,
Thank you for the 'heads up', i am not familiar with uploading videos on youtube.
I love your picture with the little steam boat pulling you in the dinghy BTW, you must be a real craftsman to make such magnificent models.
Did your friend try increasing the strength of the inlet valve spring? it made a big difference to how mine runs, maybe this would help him?
Kind regards and thanks
Ade