If you have a fuel filter, replace it or remove it. They clog up over time.
Make sure the gas cap is venting properly.
There is usually a screen on the tube that protrudes into the tank from the pet-c*ock. Look into the gas gap and see if you can see it, and if it is clogged. If so, remove and clean (be careful not to strip anything - tanks are expensive).
Could also be related to something in the carb not working right. Not sure if that model has an acellerator pump to squirt fuel in when the throttle is whacked open, but too much or not enough fuel could make it stall.
Also, if the problem is worse when the bike is hot, it might be related to your valves being too tight. Usually the bike won't idle and is hard to start hot if the valves are too tight. If it has been a long time since you checked your valves, they will tighten up with wear and will cause poor low speed running and hard starting.