I was getting some rough running and engine kills on braking, so I figured my floats were out of spec, since I've had that problem recently. Turns out that the screws that hold down the pivots of the carburetor floats weren't tightened enough, so they were allowing the floats to rattle around all over the place. I tightened the float pivots down, readjusted the floats, and got the float levels spot-on again. I took the bike for a nice, warm night ride.
Warmed up slow, but only as slow as expected for the GS500. No more misfires or "backfarts" through the airbox, all through the engine temp range. Ran much smoother, slight surging at speed was gone. However, I still have a bit of "idle dive"--when fully warmed at a stop with the choke off, the idle stabilizes at 1300 RPM--barely within 1200+/-100 RPM spec. However, if I'm tooling along, pull in the clutch, and brake to a stop, the idle "dives" to about 900-1000 RPM (very steady but slow), and then slowly crawls back up to 1300 RPM. Blipping the throttle does nothing to speed this process, and my choke/throttle cables are fully operational. I checked all my hoses and boots, and I couldn't find any kinks or leaks. The idle dive is only enough to kill the engine if it isn't warmed up.
Anyone have insight? (http://img.photobucket.com/albums/v353/Gleanerizer/idunno.gif)