I rebuilt the master clutch in my D2 last summer and all went well.  When I tried to use the tractor this weekend, I shifted into reverse but I couldn't shift it out of reverse.  I took the clutch inspection cover off and disconnected the lock-out linkage and moved the linkage rod rearward and I was able to shift the tractor out of reverse into neutral.  I think that I only need about 1/4" of additional linkage travel to unlock the transmission.
Is this lock-out adjustable?