1457 with Weber Carb - Dies if you don't pump the throttle.

I thought this would be the place to find an answer to this.

My 1457cc Mk1 has been laid up for a few years now, used to regularly run it (with no issues) but it has been left for over a year now.

It starts, but dies within a few seconds unless you constantly tap the throttle, which i'd imagine is the fuel being 'pumped' in via that action after looking with the intake off.

I'd imagine the 'cruise' jet (if it has such a thing) is blocked, hence why a constant throttle position results in it dying.

The carb is this one which replaced the Solex 1B3:

http://www.golfmk1.co.uk/images/Carbs.jpg

Could someone tell me where I should be looking/which of the many 'screws' is the thing I need to clean?

The in-line filter up from the tank is clean and I'm going to replace all the fuel pipes in the engine bay. The fuel pump pumps fuel through.

Had a look through the forums but not found anything like the problem I have.

Thanks