I thought I should follow up, albeit a little sheepishly.
So...I spent yesterday tearing everything apart, inspecting, cleaning, you name it.
Now, I'll be the first to admit if I did something wrong. I was kind of hoping for something stupid, and I think I found it.
I pulled the petcock, disassembled and inspected, all good. Went through all the lines again, manifolds, clamps, coil connections, and finally, pulled the carb to check my previous rebuild. As I was taking it apart, I noticed a rattling from the diaphragm. The plastic cam lock that holds the needle was loose. It is possible I did not lock it in place all the way, which would explain why it ran fine for a while, until it didn't.
Put everything back together, bike is running fine. In fact, rode it to the office this morning. Seems a little cold-blooded (in the 50's this morning), so maybe a little more fine-tuning is in order, but otherwise, I'm back on the horse, as it were.
If there's an upside to all of this, I got to know this fairly-new-to-me bike really, really well.
Thanks so much for all your help.
The correct amount of motorcycles to own is always N+1, N being the current number you own.
2005 Honda VTX1300S, 2009 Triumph Speed Triple,
2007 Triumph Bonneville T100, 1992 Ducati 900SS
Last edited by rwantin; 10-07-2019 at 08:12 AM.