Ok, a little tech update...
I received my loaner undercut trans in the mail a couple weeks ago (thanks Bwaller), but subsequently broke my hand and have been unable to work on the bike. I finally got it open now, and found some interesting things.
First, I discovered the gyst of my gear slipping problem: I mistakenly used a 550 shift fork with a 650 gear cluster, which resulted in incorrect clearances bewteen the shift fork fingers and its corresponding groove. In short, the gear could float in and out of it's mating gear without the fork budging. The two small forks themselves are well within specs, but the large center fork is .011" under. That gear was not being problematic, and having an undercut gearbox to go in, I think I'm going to call it ok.
Another strange problem: the bearing retainer that also holds the shift fork shaft in place was bent out 1/4" or so, as the shaft was forced outward by what appears to have been trapped air in the case where the other ends rests. I don't know the cause of this problem, but plan to drill a relief hole in the shaft to prevent it from happening again.
Should have it back together this evening, and then it's on to the mystery leak...
