79 kz400 carb?

need help identifying what the black hose barb is for on the carb body. right hand carb, engine side. not sure if its vacuum or egr of some sort. came off of a 79 kz400 b2. engine is good up to 3/4 throttle then dies off after that. gonna to get to the bike tomorrow to see what else i can find out

EGR? No.

Looks like a vent tube, but just guessing.

Fuel inlet

www.kawasaki.com/Parts/PartsDiagram/142600/1979/KZ400-B2

Clearly mislabeled, as the fuel line from the tank goes to a T between the carbs. Could it be the vacuum port for the Clean Air System?

I don't see any other vacuum ports in the diagram, so I vote for petcock vacuum port, so the mis-labeled hose would go from there to the petcock.

ill rip into tomorrow, ive looked at some other pics and it could possibly lead into the vacuum chamber for the diaphragm. ill get better pics and post

since i run a manual petcock i should pliug it

Yes.

Thanks guys, i put a new vacuum cap on the port and it does run better. was able to put 30 miles on it in todays 40 degree weather. rpms slowly drop at full throttle in 6th gear. looking at the breakdown of the carb jets, it shows a main jetsize 70 and lists a 2nd main jet size 90. bike is running uni filters with short exhaust. if its a simple fix id like to get her fixed before looking at mukuni's for it.

picking up solid carb mounts and making support brackets if i can get these straighten out. she has been a fun bike and i need to make sre she is up to par before passing her on the the girlfriend.

Go to the link in my signature, bottom of page 12.


.

Thanks, looks like i have some good info to read up on

As Ed said, I think it's a vent tube for the bowl. Sealing it off will affect the mixture.
It should be left open to atmosphere.

The parts photo show that it originally had a hose going downward, probably ending open near where the bowl drain tubes (which may also be the overflow tubes) end up.

(I don't think the fitting in question is an overflow, since gas would pour out of the carb throat before going out through that port.)

I also doubt it would be a vacuum tap being on the upstream side of the slide, and also upstream of the throttle plate. Manifold vacuum, for vacuum petcocks, must come from the downstream side of the throttle, in this case, the butterfly valve, which is right near the outlet of the carb (not the choke plate butterfly, which is on the inlet of the carb). Most likely, the vacuum ports for the petcock would be on the rubber manifolds, or on a port closer to the outlet of the carbs.

found a hairline crack in the right carb body, thought it was casting marks but zyglo confirms its indeed cracked. ordering a set of 30mm mukunis to replace the keihins.