Running idle problem

Ok just picked a 1982 1.1 up

The problem is, it wont run properly unless the choke is on

It doesnt idle unless the choke is on, and when at say 50mph, if you put choke fully off, it runs but ya can feel a slight jerk, but when ya put choke on about half way its ok

What could be causing this

check fuel filler neck for rust.

The Mk1 Golf Owners Club