New D5 owner - clutch issue

Hi all. I just acquired a D5 direct drive 94J serial. Cranks great but I am working my way through brake, clutch, steering adjustments etc. I am working on the main clutch (hand clutch). It does not lock in when I pull it back so I have to hold it to go. I thought maybe it needs adjusting. I am told it should lock in the engaged position (back toward operator). I drove it up against a pile of dirt and when some load comes on it the dozer does not move or bog down even though I have the clutch pulled back.The yoke and threaded bolt in the hand clutch linkage are all the way up and no further shortening can occur. I took the linkage off to look at it and found the clutch lever moves freely. Indicated by the red arrow in my attachment. I though this would be spring-loaded or something. I can turn it nearly 180 degrees with no resistance. Any advice would be appreciated.

I don't know anything about the D5. I do know that having a set of manuals for your machine is very worthwhile.

That model has an oil cooled clutch. Adjustment is made after removing the access cover to the clutch. Messing with the external linkage is not how you go about adjustment. What your arrow is showing is the transmission lock out mechanism, you don't want to get that out of adjustment. A set of manuals is a must.