Don't think that's your problem. I have the same MDL clutch actuation set up in mine and, as I think the instructions said but would have to check on this, left the spring off the pedal. My pedal returns all the way no problem.
Again I would have to look up the instructions as I put mine in 9 years ago, but I'd be looking at the turnbuckle gizmo that provides adjustment of the mechanism.
You got all the air out of the system, didn't you?