Went to the stealer and scheduled a return service - they actually didn't hassle me too much so that was good... They said I would have to restore the bike to stock before they would look at it though.
So I turned the fuel screws back in half a turn and re-synched the carbs (leaner than before, but rich enough to eliminate the popping) and reattached the smog stuff. Since I was messing with vaccuum line connections anyway I started testing stuff with my vaccuum gauge and pulling off vac lines to see what would happen and I found that when I pulled one of the vac lines, held the throttle open, and then closes it rapidly, the engine would die just like it had been. hmm... Okay, hooked up the stock stuff as tight as I could, including a new squirrel condom and went for a test ride. Died. Okay, that didn't work. So I pulled the smog stuff off the rest of the carbs and intakes and replaced them all with new squirrel condoms. Fired her up and her idle was way smoother than it had EVER been. hmm... Took her for a ride and she ran great and didn't feel like she was going to die as the rpms dropped, and most importantly didn't die at all. Went on the freeway, fully expecting it to die when I pulled off again but no, she kept running. Back onto the freeway again and off again and she still kept running. I got her home after an hour and a half and no problems at all. <knock on wood>
Here's my current theory: The root cause was a vaccuum leak at the one squirrel condom that was in place and another at one of the smog line hookups (they were both a little loose). When I pulled the smog stuff and jumpered the carbs and intakes with vac line I used some old, low quality line I had laying around that itself was cracking a little bit and didn't form a tight seal so I still had a vaccuum leak even though I was blocking the vac ports differently - my new seals still weren't good enough. The problem was made worse as the bike warmed up and the rubber expanded faster than the metal fittings makign the connections looser still.
The leaks weren't severe enough to really show up under constant throttle but when I was experimenting with the vaccuum gauge I found that when getting off the throttle, the vaccuum drops way down before coming back up and steadying out so when I was pulling up to a stop and closing the throttle, the vaccuum dropped and the minor vac leak was enough to drop the vaccuum just enough more to kill the engine. Ah, all I needed was a little science.
So we'll see - I'll keep testing it this week and if it's fixed, great, and if not, well at least I've got a service appointment this Saturday. I'll keep my fingers crossed that this is it. Wish me luck.
