I have a belarus as250 that has apparently had a aftermarket power steering put on it. The steering locks up under a load or when turning too sharp/fast. The steering system take pressure from what I assume is a proportioning valve then runs directly to the cylinder. The cylinder has what seems.to be an integrated demand valve that detects steering inpur and applys presure in the desired direction. I would post pictures but it seems to be restricted? Maybe i havent posted enough? Has anyone seen a steering system like this?