Sounds like the same problem I'm having with my 92. It's been sitting in the dead zone at the shop for 5 years, I picked it up, cleaned teh carbs and put new battery and plugs in it, it started right up and idled clean for about 15-25 seconds, then it just drowned out and die. It starts back up, reluctantly, and it drives fine at high speeds, but soon as it gets below 4k, the bike runs like complete piss and dies. My wiring seems to be clean and fine. I'm in the course of running through everything, I've found out my timing is off about 6 degrees, or a tooth, whichever, I'm attempting to put a new ignitor box on it, and also a new set of carbs. The motor has already been gone over, valve adjustments, new rings, new valve springs...so I'm pretty much ruling out motor problems, your problem as well as mine seems to be either electrical or fuel related. I just ordered a set of 16 viton o-rings to rebuild my carbs, they all looked decent, but I'm replacing them anyways. Might want to go to your shop and get a better 411 on what your bike is doing, Cheers!