There is also this demonstration which helped me some but I never thought about adjusting the screw stops.  Seems like a good idea if you want to change the amount you move with each flick of the lever against the stops.
YouTube - Kubota B7610 Quarter Inch Valve versus Position Control
	
		
			
		
		
	
				
			YouTube - Kubota B7610 Quarter Inch Valve versus Position Control