Have you changed out the fuel inlet valve in the carb? I'm guessing you have the OEM Mikuni carb. If that is the case, then you will find it doesn't let enough fuel into the carb bowl without the pressure a fuel pump provides. At highway speeds, climbing a hill or against a head wind is when I would hit the fuel starvation issue. Most times around town, no problem, but when on the highway it would die out. Not a very comfortable situtation.

I don't have the part number right now, but quite a few of us switched ours out for a larger Suzuki inlet valve that fits our carb. It is in some of the threads on this issue.

Also, quite a few have cut down the main petcock tube so as to get the main fuel setting to run down closer to the 'low fuel light' coming on. Otherwise there isn't enough gravity pressure to feed it until then.

Hope it helps.

Ratl.