Why did this fix my problem vapour lock?

Hi I've had a problem for couple of weeks my scooter idled fine but when I twist the throttle the engine died. Couldnt figure out what it was only 2500mls everything seemed secure. But I thought it must be something silly.
Today I was looking around the engine again I saw a rubber line coming from the bottom of the carburettor which made its way to the bottom of the engine pointing to the ground and it had a screw at the end.

I thought what the hell I'll unscrew this see what happens so unscrewed it 3/4 turn and petrol started to come out I let the petrol flow for few seconds then tightened the screw.

I started the engine and straight away it sounded better I twisted the throttle and the revs rose and rear wheel spun so seems fixed going to take it for test ride obviously I'm over the moon but going to have to put new gasket in belt cover cause when trying to figure out problem took off Cover and tore gasket!

Anyone tell me why letting petrol out fixed problem was it a vapour lock, also what is the name of the rubber line with the screw in the end. Thanks Please see photos line is one with pencil pointing to it and spring around it.

 

I'm not certain, but I think it's just a float bowl drain? As to how that would fix it - You probably had something gumming up the main jet and when you drained the fuel out it moved.

Don't sweat the cvt cover gasket, not really necessary. A lot of people run GY6 engines without a cover at all.

 

Thanks for reply I have a Chinese Haynes manual but doesn't give torque settings I'm looking the torque settings for the nuts on the drive belt cover?

 

Just tighten them so the cover is flush, doesn't matter much. Spec is probably like 4-6nm