What are these holes for?

[oldsecret]

Hello.
I'm a noob when it comes to motorcycles. Never ridden one, never done maintenance/repair on one. But now I own one and its old plus it doesn't start.
It's a 1977 GS400 caferacer project that I bought cheap because I didn't have enough projects going on. I figured it would be fun to learn something new. Right.
So, I started with ripping out the twin BS34 Mikuni carburetor, took them both apart and cleaned them up quite nicely. Reassembly was ok.

BUT, now there's a little hickup. There are two holes or outlets that's supposed to have tubes connected to them. One on each unit. Blue circles on the picture. I have searched online and in manuals to find an explanation on their purpose but so far no luck. The red circle is where to fuelhose goes from the petcock I assume.

Can anyone give me some information please?

[chuck hahn]

Are you sure they are actually holes? As i recall there are no nipples for drains or vacuum. They are probably casted but not drilled.

[oldsecret]

I'm pretty sure they are open nipples. They're not casted.
Since they are on the "air" side of the carb I could guess they might have something to do with vacuum.
There is a vacuum connect on the front left side that has a hose going to the engine.

[zed1015]

The brass outlets are simply float bowl breathers and should be kept open to atmosphere with some open ended hose attached which either connects to the original airbox or hang down behind the rear of the engine.

[chuck hahn]

OK.. Guess i need to hit the dollar store and replace the ones that got crushed yesterday. Stuck them where i always do when riding the KZ but they blew off. Went back and they had already been run over.