When I run my CT70 at WOT for a minute or so and then come to stop at a red light or stop sign the bike will often die. It won't start up again for 1 or 2 minutes, but when it starts up everything runs great.
My first thought is a bad coil. After that, I'm thinking fuel supply is not replenishing fast enough for WOT. I pulled the fuel hose and it has a decent flow, definitely not great though. These carbs don't take much fuel though, so I don't think thats it.
I just replaced the gas cap with a new one from CHP, so I dont think a vacuum is the issue.