There's a current Tech Section thread about a missing clutch cable's barrel -the small bit that captures the cable's soldered nipple and is a pivot point within the control lever. Newish owner had an issue that was quickly resolved when the missing cable barrel was discovered. A learning experience regarding all Airheads.
I'll share another small part that is easily lost or, perhaps, is already missing thanks to a PO. Either way, without this mysterious little part, it may result in a possible loss of control while riding.
Notice the small wedge listed as #5 in the diagram. This small triangular bit of steel is what
locks the control housing/lever perch to the handlebars. There is one machine screw that snugs the housing to the handlebar. Without the wedge installed, the aluminum 'ears' that form the housing's pinch bracket can be broken, resulting in the entire control assembly rotating about the handlebar or a worse case scenario, falling off as you properly apply a counter-steering push as you enter a sporty right-hander twisty.

This is a photo of the BMW
NLA wedge. Excellent photo showing just how small this part is. You can well imagine not even missing it should you not know of its existence. Think changing out a handlebar...
Fortunately, Bob's BMW
http://www.bobsbmw.com/ sells a German-made repop for a
healthy $10.00USD. I thought about making my own until I noticed the serrations on the curved face that bite into the handlebar. The Bob's Wedgie is part #32721232929
R. Other dealers possibly may have these.

The only photo I could locate that shows where the wedge in installed is this nasty control housing offered on eBay. The white arrows indicate the install position. Note the flat areas for the wedge plus the alloy pinch ears. The fracture usually occurs to the ear under the machine screw's head. The BMW OEM wedge has a rounded notch that is captured by the machine screw, holding it in position during the tightening sequence. BTW, a new clutch-side handle unit is $89.00USD.

I do not have a handlebar housing unit that rotates but I plan to check all three Airheads just to be sure. I have a couple Wedges in the shop. All I have to do is find them.