Quick question, is the carburetor fan supposed to blow or suck air from the carburetor area? Mine is sucking air....

It should blow air to the carby. Check the wiring, it may have just been connected up backwards.

The polarity of the connections is incorrect maybe the fan is running backwards

Its a Carburettor Cooling fan hence definately should be blowing at the carb.
Also check the ducts are clear of debris.....

Thank you all! I've been checking the wiring and cannot figure out how or why the fan is sucking and not blowing. There's a red wire connected to a red wire, and a black connected to earth. No way to get it wrong...

unless the fan is fitted the wrong way around...

Is it possible to disassemble the fan??

Never tried - usually I just throw them in the bin as excess baggage... I don't think I've had a standard X1/9 after my first one (20 years ago).

Just another thought. I know you've matched the wires on the fan at the plug but that doesn't mean the wiring loom has the wires the right way around. I can't remember if the thermostat in the carb is earthed through the carb itself but I doubt it. It could still be a wiring fault. Even the wires on the fan itself could have be connected back-to-front and it has always sucked instead of blowed.

Mystery solved: the fan was assembled backwards, apparently from the factory.
The fan is actually a "hamster wheel" that spins and throws air outwards. But because it has profiled blades, it can actually suck air inwards when spinning the wrong way round.
Anyway, quick notes. Do not try do disassemble the fan to clean it, as the plastic casing will start crumbling to pieces when you unscrew it from the metal bracket. The actual "hamster wheel" can be removed without much trouble: just remove the fan and metal bracket assembly from the car, remove the inlet shroud of the fan, remove the spring clip that holds the fan and pull the fan using an Allen key trough one of the fan's holes. There's no poka-yoka to prevent the fan from being assembled the wrong way round, but one side of the fan's hub is longer than the other. Short side is outwards.

It begs the question of how many fans made it out of the factory like that!

Well done all the same

Wow what a problem