From
http://www.vintagebmw.org/current/tech/tech29.htmRemoving the Steering Stem Lock
A quick little tech tip, for those who have lost the key for the frame/steering lock on an airhead, can't find a key blank, and want to remove the lock, to replace the whole thing with a new lock and key set.
1. Take two small screwdrivers, and drive each one under the Neiman chrome lock cover, on each side of the retaining rivet. Pry the cover up, and remove it alony with the rivet.
2. When you look at the end of the lock, you will see the round barrel of the lock, with the key slot, and square box, on the top. that box is where the tumblers and springs of the lock are located. On the top of that square block, there is a thin band of sheet metal, that retains the springs and tumblers. Use an ice pick to lever the plate out, so you can grab the end of it with a pair of needle nose pliers.
3. Remove the plate completely, and you will notice that the ends of 4 springs, that push the tumblers down, into the lock, will jump up and their ends will be visible in the small open area directly above the lock. Bend yourself a small hook, out of piano wire, and reach into this area, snag each spring, and pull it out of the body of the lock.
4. Insert a flat blade screwdriver into the key slot, and use a light hammer to drive the screwdriver into the slot. Don't go crazy here, just drive it in enough that it will stick in the slot.
5. use a blow gun on a air line from an air compressor, and blow air into the key slot. This will push all four of the tumblers up, out of the lock. While you are constantly blowing the air into the lock, turn the screwdriver in a counter clockwise direction, and the lock will rotate. When you have it rotated, simply pull the screw driver out, and the body of the fork lock will come out of the frame, on the end of the screwdriver.
Simple Eh?
That is how I have removed them in /2's for years.
-Vech