One of the problems with Zenith carbs is that the lazy buggers at the factory never bothered to anneal the castings (zinc-rich 'white' or 'pot' metal) after manufacture.

I've got a Zenith 36IV carb on my vehicle, a 1972 Land Rover, and the trick with carbs that defy normal rebuilding is to "glass plate grind" them. Basically, you put a piece of 200 grit sand or emery paper on a piece of glass, add a dolop of oil, and rub the flat faces of the two halves on the sandpaper 'til they are even..

Zenith carbs have a notorious history of warping after they get goo and hot. This warping allows excess fuel to leak out of the bowl. Now usually, this isn't such a problem on an updraft carb like on the Atomic 4, but on the 2.25 litre 4 on the Land Rover, it leads to excessive fuel consumption and poor idling. Things seem to be OK at speed, tho'....

Solex purchased Zenith a few years back, but the upshot is the last rebuild kit I bought was only $24.

Compared to other carbs, this one is dead-simple to pull apart - and get back together without too many left over (and obviously unneceassary) parts. ;-) Have a go at it. A swipe or two on the emery paper will show you where the high/low spots/warps are. Sand the halves 'til the flange faces are all bright.

Cheers