Hi Derek
Thought it was you!. I see you have the "dreaded Hatta forks" on yours. I have no experience with these but that Dirt Bike test I sent you may give some clues. If you are getting only 2" travel, there may be something wrong with the set-up. Check for:
1) Forks binding up. That could be a combination of a bent fork legs/axle and/or bent fork brace. Remove the fork brace and see if the forks work better. Then loosen the axle clamps and check again. If the forks work better, whip out the front wheel and remove each fork leg. Check the straightness by rolling them on a flat surface like your granite kitchen tops (sorry love!). Do the same with the axle. If the forks are both slightly bent, a cheapie solution is to re-install them with the bend facing "backwards". That way they will both act in parallel.
If the axle is bent, best get a local mechanic or bike shop press it straight.
The fork brace should fit exactly on the mounting lugs. Any attempt to pull up gaps with the bolts may cause the forks to bind.
2) Forks full of water. Could be a mess in there..... . While the fork legs are out, remove the caps and drain them. Check if they will move smoothly over their full travel.
3) Fork springs too hard. If there are spacers on top of the springs, you can remove some of them.
Fork springs should be 474mm long (as per manual)
4) Forks too full of oil, or oil too thick. Replace oil with 175cc of SAE 10W. (as per manual)
The latest Bighorn roller ('74) I have, also has forks that seem "solid". Will have to inspect those too.
Regards
David