Looking really good, and your 'mechanic' figure's excellent! You've got that concentration on his face spot-on!
I thought there was a bit of a problem with his right hand, until I realised he's holding some kind of tool and his hand's side-on, but his wrist seemed a little too thin compared with the sleeve - then I put my reading glasses on and had a proper look.
I can't quite put my finger on why the right hand looks a little strange, but I've just tried holding something in the way he's holding the tool, and discovered that it's a very un-natural position to hold something in (my arthritic wrist and shoulder certainly didn't think it was natural
), so I'm wondering if it's because as adults we're not used to seeing hands in that position. Kids are a lot more 'bendy' though, so maybe that's a completely natural position for him. I'm not sure.