Applicability: All BMW Airhead models; with some useful information for any splines-driven dry-plate clutch.
Why do it: (1) Smoother shifting; (2) Avoid wearing out expensive parts with expensive labor to repair damage; (3) Avoid suddenly spline failure
When to do it: Depends on year model and conditions you ride in, but probably every 12000 to 35000 miles.
What are you going to do: Unfasten the transmission, move it slightly backwards, clean and lubricate the transmission input shaft splines, and then reinstall transmission. You will probably do other work at the same time, described in the text that follows.
NOTE: While an adequate job can be done by just moving the transmission backwards, a 100% job means removing the transmission from the motorcycle. THAT can be put off until you have another reason for removing the transmission.
Required Skill level: Lower intermediate or better