I have a 22 ton Hitachi UH083 excavator, with mechanical controls. My dipper arm is only retracting on low speed. When I push the lever fully over to retract the dipper, it isn’t kicking in the second pump to operate the high speed return, which is how it’s supposed to work, as I understand it. This is an older machine with all mechanical linkage. I believe it’s a linkage or adjustment issue but I don’t know where to look, or what linkage to adjust? I do not have vast amounts of knowledge or experience like many of you, so bare with me please I’d really like to fix this, because aside from this issue, it’s a great machine!
The amount of stroke on your control spool for your dipper will determine the speed at which it moves depending on your engine rpm’s, gpm’s of your pump, and the pressure required. I would first check how much control spool movement you have at the control valve as compared with say....the boom or bucket spool.
Those ran a manual rod to stroke the pumps from the control linkages for the implements. Look for lever of some sort that connects to the pumps that moves whenever you operate something. Wasn't much to those machines. That's probably why it still is operational.
just wondering if you ever got this figured out?... I had the same issue and made a few adjustments and it seems to have gone away.