Float level Zenith updraught Carburettor

[Rick F]

A7 Components stock the Zenith 22FZ handbook which very good.
The level can be measured in the tube in which the slow running jet fits.
I do this by removing the slow running jet tube and putting a length of clear tube down the hole.
The tube fills up to the fuel level.
Then close the top end of the tube with a finger and withdraw the tube.
Provided the tube is quite small bore it will keep the fuel in the tube and this shows the fuel level.
I have a tube with a washer pushed over it which is a tight fit and it is marked with the position the fuel should reach.
The tube is dropped in so that it sits on the washer and when it is withdrawn the amount that the level is out can be seen.
The level can then be adjusted by moving the collar on the needle valve as described in the handbook.
It's rather fiddly.

All the above is why my chummy-engined special has run happily on a nice, simple 24T tractor carb for the past five years!