I'm feeling pretty stoopid over here.

I'm converting a 50cc Echo short block for my brother and found a WT-463 for a pretty good price on *Bay. I believe these were found on McCulloch 46 and 49cc chainsaws. Anyway, without the engine in front of me Ican't for sure identify all the inputs. I was unable to get McCulloch's web site to cough up a manual (and believe me, I tried before exposing my ignorance). In particular, it looks like it has a crankcase pulse hole (#3) that I didn't expect. And I'm not sure what the little brass tube beside the mixture needles is for.

So, could those of you with some experience in this please indulge my ignorance and enumerate the ins and outs of this carb?

Many Thanks

KD