Clutch adjusting nut

[His Dudeness]

Impact sockets are often thicker than a normal socket so the outside diameter might not fit in the hole but if it does that's what I'd try first. An impact socket with a rattle gun.

There's also a "universal socket" that might be worth trying. It has pins in it that retract to form the shape of the nut. I haven't seen or used one before so can't say if it's any good or not

http://www.fleetfarm.com/products/images...030982.jpg