Harley Sportster: Mysterious clutch issue

So I've got an '86 Sporty that's been riding great for a few years now. Came time to get a new clutch pack, but I'm having some trouble adjusting the clutch. The issue is that, with the new clutch pack in, engine running in neutral, the bike will shift into gear, but when the clutch control is released, the gear doesn't engage: The bike just sits idling, instead of stalling out. The most telling note is the clutch spring: It didn't need to be compressed when the old pack was initially removed, or when it was replaced with the new pack in. I've checked the tolerance of the steels and friction plates on both the old pack and the replacement, and both are in spec, per the technical manual. I've even replaced the spring, twice: once with a brand new one, and once with a used spring pulled off a working clutch on another '86. Same result every time. Damn spring goes on and comes off without a compressor. What could be the issue there? The basket is not warped, blued or dinged up in any way I can see. What else could be causing this spring issue, and isn't that the root of my clutch problem?

In case I'm missing something else relevant (and because one of the best parts about having a bike is talking about it), here's everything else I've done to it:

1.Upgraded to 1250 kit. Engine runs like a champ. 2.Upgraded jet in carburator to account for bigger jugs. Insert your own pun here. 3.Dropped down back end to 10" shocks. Lowest man always wins. 4.Fucked with the wiring in order to redo taillights. Removed rear blinkers, leaving one aftermarket brake light. All in working order. 5. Added 12" apes, so the clutch cable is brand new. Adjusted the cable to TM spec, still has no effect on gear engaging.

Asked all my Harley guru buddies, and no one knows whats going on. Someone's here's gotta know how to beat this clutch into submission.