The motorbikes lose their gasoline after time without using them. Experinced on my own vanilla experimental server and also noticed by watching streamers (1.30).

And looking at Badlands streams, cars seem also be affected.

Find a motorbike, fuel it up, leave the server, come back the next day and its out of gas. Happens for both, the mopeds and dirtbikes.

Thanks for looking into it.