Some petcock questions for a CB700

[polar8]

I'm trying to get a CB700 running that has been sitting for a year. I drained the tank and filled it up with new gas, but now I can't get it to flow out of the petcock, whether it's on the On or Res position. I took it apart and I am soaking the body in gas to see if there is some gunk in there I can loosen. Any other suggestions?

Also, when I got the bike there was a black tube that went from the petcock to somewhere near the carburetors (in addition to the fuel tube) but had fallen off the petcock. I looked it up on the fiche and I think it's the "petcock vacuum tube". Problem is, there are two connections on the petcock, and I don't know which one it connects to. I've labled these two connections 1 and 2 in the picture below. Thanks!

[muttstang]

don't know off of the top of my head, but a quick way to check it is to pull the fuel line off and set it up to drain into a cup, then attach a hose to each vacuum fitting and suck on the tube.  fuel will flow if you have the right one.

though I'm sure someone will chime in with the proper nipple to use

[polar8]

Very interesting. So what exactly does that tube do? Could it being disconnected have something to do with fuel not flowing from the petcock? Although I was under the impression that fuel should flow freely while in Res mode, even with the tank completely disconnected from the bike.

[Tryvelcro]

Try the pic in this thread, might help you:

http://nighthawk-forums.com/index.php/topic,7929.0.html

Although I was under the impression that fuel should flow freely while in Res mode, even with the tank completely disconnected from the bike.

Gotta have vacuum if you want fuel flow.

[chromy]

Gotta have a vacuum line connected to what you've labeled as connection #2 (in your pic in this  thread) to the vacuum port on the #2 intake manifold (between engine and #2 carb).  Engine turning over creates vacuum which alows fuel flow through petcock.

Good luck!

[polar8]

Ok, got it. To test the petcock when the tank is off the bike, I could simulate by sucking on that vacuum tube correct?

[ExTex]

Yes, or use a turkey baster, large syringe or minivac.

Vacuum is need for fuel flow in either ON or Reserve positions.

Ride Safely,

[chromy]

Ok, got it. To test the petcock when the tank is off the bike, I could simulate by sucking on that vacuum tube correct?

Yes.