While I was replacing the air spring O-rings in a customer's early-21st Century Cannondale F600 I noticed that the fork boot had a rip in it. The Headshok has many fine qualities, but it all goes to hell if the boot does not remain sealed against contamination. The needle bearings on which the fork slides so smoothly get all gritty and crunchy. Then you have to rebuild the fork. That will force you to face some of the more vexing idiosyncrasies of the design.
I had not done a boot replacement in years. The last Headshok that needed a boot was on a bike already so beat that my field-hospital repair was good enough. I cut a section of inner tube and slid it down to cover the tender parts. But a little research found a source for real pleated shock boots with nice little clamps, at a place that styles itself as "The Cannondale Experts."
When the boot arrived yesterday I knocked the fork out of the frame and started trying to work the boot down over the large diameter outer tube of the shock to reach the skinnier part it is supposed to protect. The boot has a large end and a small end. Unfortunately, the small end is supposed to go on the bottom, making the boot basically impossible to stretch over the larger diameter seat at the bottom of the upper tube, where the larger opening gets fastened when the boot is in place. Lubing it and working gently with various blunt objects was getting nowhere.
Not to be defeated, I turned the boot inside out so I could lead with the large opening. Once I had it down on the skinnier part of the shock I was able to roll it back right side out with the help of one more blunt object. Ta daah!
I looked on line today and all the advice I saw said you have to tear down the fork to change the boot. But in case you don't want to bother, do it the wrong way. It worked for me.