I've done that 'adjustment' on several 750s, including the one on the cover of my book, for riders with pants inseams shorter than 31".
To undo it:
1. Centerstand the bike.
2. Loosen the 4 nuts on the bottom of the forks that hold the axle in their saddle.
3. Loosen the lower triple tree's bolts and pull one of them out of the tree (you'll do this with the other one later).
4. Loosen the top bolt of the fork where you removed the lower triple tree bolt, push that fork back down into place and snug the top bolt enough to hold the fork.
5. Put in the lower triple tree bolt for that fork and snug it down (not fully tight yet).
6. Remove the other lower triple tree bolt and repeat step 4 with this fork.
7. Tighten the 2nd fork's lower triple tree bolt, then it's top one.
8. Tighten the lower, then upper, bolts on the other fork.
9. Tighten the axle cap's nuts. Do this by tightening the flush side first on both legs, then the gapped side second.
A note about the axle caps: if the 750 is made before 12/72 (check the label on the steering head) the 'gap' in the axle clamps may be forward instead of at the back. This is/was normal (my first 750K1 and my current 750K2 11/72 build both have the gaps at the front. Not all do.) The difference is attributed to the type of damping parts used inside the forks. If you know yours: if you have the 3-piece damping collars on the bottom of the fork leg, the gap goes forward. If there are NO damping collars visible (because they are inside the later legs) the gap goes backward.
Warning: this has sparked controversial arguments here in the forums...but it is also true.
