There are probably other posts on this topic, but I couldn't find any by searching, so I thought I would share what I just learned here:
When replacing the levers on my 2000 M900 (this also applies to the S2R 1000, and others), I needed to swap the clutch plunger and barrel out of the stock lever and onto the aftermarket lever. The plunger is the brass pin that actually pushes the rubber master cylinder boot, disengaging the clutch. Note, there is a 1.5 mm Allen lock screw holding the plunger on the bottom "end" of the barrel. Mine was totally siezed. Nothing worked. After several rounds of soaking in liquid wrench, I used a propane torch to heat the lockscrew. Voila! It came out so easily I thought for sure I had stripped it. A little more heat, and the plunger unscrews just as easily from the barrel.
Hope that trick saves a bit of time for the next guy!
Good job! [beer]
A somewhat industrial heat gun will get 'em hot enough.