Yamaha Aerox 2007 - not getting fuel

Scooter did not ignite whatsoever after lots of attempt. ( +3 degree C)
Spark is ok, spark plug is dry.

I loosened the two hoses coming from some kind of valve below the tank. By sucking the thinnest one fuel comes out of the other thicker one. By doing this with the thicker connected correctly to the carb, the scooter started quickly.
While holding one finger onto the smallest hole on the carb, I can feel a little vacuum. I suppose it it too weak. The metal thing below the tank must be some kind of vacuum valve, maybe with fuel filter too?

And there must be some kind of function in the carb that is making the vacuum to the thin hose, that I conclude is too weak. Or am I misunderstanding something?

Does anybody know how this works and where the problem can be?

The autochoke was replaced last summer. The scooter is a little problematic to start in the summertime too, the longer is was standing still the harder to start. Tree days unused makes 20-30 seconds necessary on the starter.

 

Sounds like it's loosing compression possibly.
You need to get a compression tester on it.
Also it could be the vacuum hose has a tiny split in it? Maybe?

 

I haven't been suspecting compression as the scooter has good power. I understand now that the vacuum is produced by the compression /piston. Though, I have added some oil in the tank in addition to the automatic oil pump system. The exhaust is quite smoky .
I have been thinking that maybe vacuum valve opened only when I sucked manually ( strong) , and there is a leak in the vacuum hose or inside the vacuum valve

 

Normally when the valve is faulty it won't work at all, or it just pours out constantly.
Could be the intake manifold leaking?

 

I am not sure how to locate the intake manifold..?

 

It's what attached the carb to the engine. The rubber part.