Just got a pair of NOS Dellorto DRLA 40's.
These carbs do not have the air bleed screws for synchronizing. The ports are there, but they do not look like they were drilled or tapped for the air bleed screws.

The date stamp on the bottom of these carbs show 7/93.

I inserted a small hose in the port and could not blow any air through. I'm convinced they were never drilled.
I tried to get a photo inside the barrels to show that port is not drilled through, but
couldn't get a clear view.

Did all DRLA's have the air bleed screws, or were they just on early models?

Click to view attachment

Hmm mine have the by-pass screws right next to the idle mixture screws on both pairs I have.

.........SHOW a side VIEW of the carburator(s) where the adjusters are supposed to be..............So we can help you......M.M.

bump
photo added

..........Thanks for the photo, it helps.....I have never seen this before eighter.The bypass air screws are just not there.....Well maybe this IS an update from the factory.....Do take note however .....most of the installation and tune up instructions, adjustments, I have read, WANT the Idle bypass screws --SCREWED IN ALL THE WAY.....This effectively disables the AIR BYPASS SYSTEM anyway.(rendering that part of the system useless anyway)....With the proper venturis, air correction and main jets the carbs will run just fine.........M.M.

I've read the same things about tuning, I don't have a four port mercury gauge anyhow. I just want to validate these are authentic. I was very excited to find them. They are brand spanking new (sitting on a shelf for 17 years) still in the Dellorto packaging.

yes, Dells are THAT good.

Congrads on scoring the brand new Dells. I was a die hard Weber guy and hated Dells until I was told and convinced that Dells were better. I got a pair even though I had a pair of 44 Webers and found out that they are indeed better especially in the progression circuit.

In your pic the ports you have circled aren't the air by-pass. They are the ones right next to it. You usually don't need them and just leave them closed.

I understand that, what I'm missing are the air bleed screws.
The air bleed screws are designed to be used with a four port gauge to fine tune the air by-pass so the carbs are exactly balanced on each barrel.
Like Webers, you can just leave the air by-pass closed, but Dells had this nice added feature where you can actually tune them in with the use of the four port gauge rather than on a flow bench.
It's a feature most never use, they just get them close with a snail, but I was curious to know if others had Dells like mine where this port was never even finished.