Hi fam - I have a 94 GS500E, and I've been having some issues lately. I'm at a stop light, it turns green, I shift down into first. As I'm trying to accelerate, the RPMs don't increase much, and I have a heavy clunky bogg in my bike, jerking me slowly forward at no more than 15mph. Eventually it will catch and launch me forward and ride fine. It doesn't happen every time, but it's enough to be worried.

Any ideas what I could be dealing with? Clutch? Transmission? Is my shift/launch technique bad?

Sounds like a clutch issue. Probably just a misadjusted cable. Since the clutches on these bikes are oversized for 500cc and rarely wear out (when treated properly) you probably just need to re-adjust the cable using the 3 point method. If you find that you frequently have to re-adjust the clutch you may need a new cable.

Procedure covered here:
http://wiki.gstwins.com/index.php?n=Maintenance.AdjustClutch

There are probably more in-depth instructions with pictures in the Clymer or Haynes repair manuals.

My 89 used to do this when some genius decided that since the air jet was 42.5 he installed a 42.5 pilot jet in it.
Bogging when demand = rich. If the bike used to run right before - look for either a pilot or mains that's come unseated and is loose as well as a float that's drifted high. Diagnose first. Float is U tube, easiest to check. Then observe as you take things off to correlate to the problem you're having. The 89-00 carbs tend to drift their floats high. If you take the carbs off and find nothing out of whack check the butterflies for synch as well as a stuck choke or something.

Now clutch cable if its going loose cos threads in one fitting or another are wearing and letting it get out of adjustment will likely feel very high in play at the lever, and will not disengage when you pull it. Seems to me like you're not having those problems. Clutch that's worn will slip under load, so almost the opposite problem.

Cool.
Buddha.