I finally cleared the garage so I could work on the DR650 (I had to finish parting out a Multistrada). Briefly, this is what I found, more or less in order of operation. BTW, the Carb is a TM40 and its a 'normal' petcock, not the OEM vacuum job.
1) fuel flowed from the petcock and through the filter in either 'run' or 'reserve'. It flowed faster in 'reserve'.
2) Shining a light into the tank was illuminating. I have never seen so much sh*t in a gas tank before. Miscellaneous debris of various sizes, colors, and textures. Color was murky too. Keep in mind that I put a well cleaned IMS tank on last fall and have only run 5-6 full tanks through it. I must have gotten the filling station's dregs the last time I filled the tank.
3) The carb looked surprisingly clean since I haven't done a thing to it in the 8,000 miles that I've owned it. I cleaned it anyway.
4) fuel flow was much improved after cleaning the petcock, gas tank, and replacing the filter.
After doing the above work, the bike fired up after a couple cranks. I test rode it to a gas station and back home. All was good so I took one of my sons for a 80 mile ride in the coast range and the bike worked flawlessly. Well, except for the missing side cover, but that's another post.
Thanks for the replies, I'm not much of a carb guy so the TM40 with all of it's jets and holes seems intimidating.
BTW, what do you do with 3.5 gallons of bad gas? Weed killer? BBQ starter? Give it to an annoying neighbor?