[yetibone]

It's a real trial-and-error prosess when setting up carbs to suit an application. We are running Dellorto DHLA 40s on Hummbug. I got 'em off Ebay for a smokin' deal though. It took me about two weeks to get the mixture right thru adjusting float levels, reaming the mains, and getting smaller idle jets, and smaller emulsion tubes.

I've got a Triumph TR6 that I installed 3 Dellorto DHLA 40s on
(got them from the same fellow on Ebay) I went up in size on the idle jets in .05mm incriments to fix the same situation that you are experiencing. Once I got to .65mm, I found stoichioimetric.

Try to find a tool seller who can provide you with a good set of jet reamers, and guages to measure them with. I got mine from CB Performance. They are far cheaper than buying jets in the long run.

If you have one cylinder that is leaner than the rest, get the engine to operating temp, remove the air cleaners, start the engine, and set three fingers together on one of the velocity stacks. Does the idle go up, or down? If the idle speed drops, then that cylinder's mixture is OK. Try another one. If you find one
cylinder that will make the idle speed rise by blocking the air going into the velocity stack, then that cylinder is lean.

Like you said, possibly a blocked progerssion port.

Yetibone