I'm wondering what this nipple is used for? There is also one 180 degrees opposite of the main carb barb. Does anyone know what that is for? What should I do with both of these "extra" barbs? This is a 3W78 twin BTW. I bought it used and it did not come with a manual. Thanks and here is a picture of the barb on the side, the other picture did not come out well enough to post.
Tim

Doc,
The silver one is for fuel. The brass one on the pressure regulator cover is to be connected with a hose to the fusalage interior. The reg needs stable pressure to provide proper fuel metering.

Dave

The diaphragm works with atmospheric pressure...If air is blown against the diaphragm it upsets the way the diaphragm works...A piece of fuel tubing from the nipple shown through the firewall keeps air from blowing against the diaphragm...
the only barb needed is the one in the carb body that connects to the fuel line, others were added by a former owner...

Thanks for the quick replies, I would have hooked it up wrong. The other barb is on the opposite side from the brass barb, should I close it off somehow?
Tim

This is an out-of-focus picture of the other barb that I'm asking about.
Tim

That looks like the pulse nipple.If its on the same side as your idol adjustment screw.It would connect to a nipple off the engine crankcase.This is what operates your fuel pump diaphram.


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