Direct Bikes Ninja Stalling

[AMTF]

Hi everyone,

I bought a 50cc Direct Bikes scooter, and it has a problem with stalling. It would cut out after around 20 seconds when I first got it, but after cleaning the carb it runs for a couple of minutes. I have checked the valve clearance and its OK, set to 0.002. It will stall when releasing the throttle. There is a second pipe coming off the exhaust which isn't connected to anything. What should I try next?

Thank you,

Alex