Weber throttle shaft (40 IDF )

How does the throttle spindle seal where it goes through the carb body?. Does it just seal on the bearings at each end?. Are they easy to change?. I figure mine must be worn as I seem to have an induction leak on number 2. Used the LPG down the carb trick to find the cylinder responsible. All the vacuum hoses are air tight and I think the shaft might be a bit loose.
Any suggestions?.