Machine is a Komatsu PC27-8...3 ton approx., early 2000 year. Plumbed from factory for auxiliary attachments. Ram on thumb is double acting. When I plumb it one way it functions in both directions, but has very little downwards pressure. Swap lines to the cylinder ports and it has great downwards pressure but doesn't open. I'm guessing my auxiliary is only a loop with pressure in one direction (as I can only see one line jump when I work the valve)? I'm thinking I need a single acting cylinder that I only plumb with the pressure side as the internal spring will open it back up when I let off with the pressure? Any one have any ideas? Thanks much!