I couldn't find a chart like there is for Webers, but I found some DHLA information
The emulsion tube is a mix device (mixes air & fuel together) It basically controls the A/F mixture at all except near-idle and full-throttle. It takes fuel from the Main jet and air from the Air Corrector jet, then adjust this mixture further depending on airflow & acceleration
The Weber book says: "The controlling factors of the emulsion tube are its diameter and the location of the emulsion holes...the numbers do not follow in any particular sequence which would indicate the applicable characteristics"
First choose:
* Larger cylinders: smaller numbers
* Smaller cylinder: bigger numbers
* Running alcohol (E85) instead of petrol affects the initial choice
Cylinder capacity Suggested tube
250-325 7772.8 A12
275-400 7772.7 A12/A15
350-475 7772.6 A15
450-575 7772.5
Fine tuning:
* Low rpm enrichment/Slight acceleration enrichment: holes toward the bottom
* Low rpm leaning/Slight acceleration leaning: holes toward the top
* High rpm leaning: More holes
* Low rpm enrichment: smaller diameter tube
Jetting program for Weber DCO and Dellorto DHLA carbs
http://www.dvandrews.co.uk