If this was my bike, I would take a very careful look at the needle and seat. There could be some debris holding the needle open. Also I would look very closely to see if the float moves up and down without sticking. And then I would look closely at the float itself to determine if it is waterlogged. ( actually gas logged ) If every thing looks better than perfect, then I would check the float adjustment, but it has been my experience that the adjustment does not usually change. Look very close and careful.
But since this isnt my bike, what do you plan to do ?
Keep us posted on what you see and find out.
John