If they suddenly got slow it may be the valve in the top of the block. To access it remove the dump valve (on right of seat) then remove the two studs holding the egg shaped plate .Under that you will see a screw cap. Carefully undo it as it is under spring pressure, remove spring taking care not to drop anything inside then you will see a valve like a cup, cut out a piece of wood push it into the cup and slide it up and down to free it. Thats what I did anyway with a similar problem.
John, January 2009
