Dolkita EA7900PRZ Carb Question

[HandLogger]

I'm sure that I've griped about it before, but we purchased a new Makita EA7900PRZ over a year ago and, long story short, it hasn't seen its first log yet. Apparently, it has the fuel metering issue that I've read about - more than once - so I ordered a new Zama C1O-DM11D to replace the factory junk and put the saw on a shelf in a cargo container.

As we now have a fairly large tree removal job coming up soon, I really need the saw again, so I've pulled it out and am presently in the process of performing the carb replacement. Although it's not shown in the Makita EA7900PR Parts Breakdown manual, the factory carb has a brass elbow attached to the bottom cover [which I assume is a diaphragm cover] and a hose that attaches to it. I'm no saw carburetor expert, so I have no idea what the hose does ... but the real problem is that the new Zama C1O-DM11D does not have the same elbow attached to the bottom cover.

I suppose it would be simple enough to simply swap the covers, but I wanted to check with those on the ASF with lots of carb experience first. With my luck, I'll make the mod and be sorry for it later.

Thank you kindly for your time.

EDIT:
I though it might prove useful to add a photo of the two carbs in question. As mentioned, this is the bottom view of both units. The carb on the left is the factory unit that floods like NOLA in '05, if breathed upon, while the one on the right is the new Zama C1O-DM11D that provides two nice simple adjustment screws. Other than that - and the elbow I'm asking about - they are nearly identical. I have also discovered that the Zama part number for the factory unit is C3M-DM18A. I was just looking at the Zama parts breakdown for this carb and, unfortunately, they don't describe what the elbow is used for. Considering that it's clearly on the metering side, is it a possible setup for a primer bulb? Unlike our EA6100P, the EA7900PRZ isn't equipped with a primer bulb, so I'm still wondering why this elbow is here?

 

[HandLogger]

Okay, so there's some new information in this regard. The fellow we purchased the new Zama carbs from has informed us that they are actually the C3M-DM11D type: not the C10-DM11D models. Apparently, they were shipped out to him in the wrong boxes and a close visual inspection proves the supplier right.

In other words, here is an important correction to the original post: The carb pictured on the left is the flood-prone factory Zama C3M-DM18A, while the one pictured on the right is a C3M-DM11D.

I was also told that the elbow on the bottom of the newer factory installed Zama C3M-DM18A is merely a vent for the metering diaphragm. As I didn't get that information right away, though, I went ahead and swapped the plates out. After some fiddling with the carb adjustments on the replacement C3M-DM11D, I was finally able to get our new Makita EA7900PRZ running. Much like the MS660s we've employed over the years, it looks likes the big Makita will be a "hard starter," but I'm happy that it's running, nevertheless.