The speedometer cable boot on the BMW Airhead often gets cracked and dry and stops doing its job of keeping water out of the transmission. It also looks like crap. It is actually a pretty cheap and easy fix. Here’s how.
Start by turning your new speedometer cable boot inside out and working it onto the end of the cable. Not shown here, but very important, first slide the old boot up and out of the way. Don’t remove the old boot yet just in case something goes wrong installing the new one. Better an old boot than no boot at all. Also important and also not shown….remove the back bushing (if present) on the end of the cable before slipping on the new boot. It will be impossible otherwise.
Carefully slide the new speedometer boot up the cable. It looks easy but the whole thing is actually quite stiff AND you risk kinking the cable if you push too hard and bend it. Some dish soap (a tiny bit) might be helpful here
Now you can pop the speedometer boot back to its normal direction, or right side out, or whatever you want to call it. It looks less shiny and more voluptuous in its proper direction. At this point you can replace the black bushing and reinstall the cable into the gearbox.
Carefully cut the old boot off with a sharp knife, and away you go!