Petcock question

[Gene]

 I have a 85 CB650sc. It came with a PCV valve, a charcoal cannister and perhaps other smog equipment. (disconnected) On the left side, it has a vacuum-operated valve. On the back is a another nipple, I'm guessing it's somehow connected with the PCV valve, or charcoal cannister.  Does anyone know what that nipple is for?

BTW, I would like to connect the PCV valve and cannister back up, but the info in the service manual are minimal. Anyone have any information?

[Pete in PA]

On the contrary, If I got stuck with a cali bike I'd remove ALL that junk.

On the fuel petcock there is a nipple for the vacuum line from cylinder 2 and one that has no tube for air pressure to enter.

No emissions stuff attached to the petcock.

[mollusc]

Are you sure it's a connection nipple and not just a breather?

[Gene]

Mollusc,

If the nipple is a breather, I'm not sure why.

Everything considered, I'm going to leave everything alone.

[Bob H]

I have a 85 CB650sc. It came with a PCV valve, a charcoal cannister and perhaps other smog equipment.

Not the same model as yours - but my California emissions equipped 750 had a pile of spaghetti noodles going to and from the charcoal canister. Even the gas tank vent to atmosphere, and the 4 vent tubes from the carb float bowls were associated with the charcoal canister via at least 2 valve control things.

One of those valve control things was described in the manual as "PCV" valve which we typically would consider Positive Crankcase Ventilation - but it was a Purge Control Valve and that same valve was given different names in different diagrams. I was driven to drink.

My experience was outlined here, and there is a video that may help in that thread if you do decide to yank the stuff. For now I would just be curious what happens to that unknown petcock nipple when the bike is running, and you put your finger over it. As long as it isn't sucking air (vacuum leak) and the bike runs OK then I suppose you could leave it alone.


https://nighthawkforums.com/index.php?topic=214.0

[Gene]

 Thanks Bob. As far as it "sucking air" on the petcock, I can't see how it could, since it's not connected to anything but fuel but I will check it out anyways. Perhaps it is supposed to go to the vent(?) fitting on the tank.  I took a quick peek at your smog equipment adventure, and besides mine being a 650, I think they are very close to being identical. Thanks for your work. BTW, on mine, all the smog equipment was disconnected by a previous owner, except for the crankcase vent to the airbox, which I see no reason to disconnect. However, the rest of the equipment is still there.

[mollusc]

Even the non-California bikes vent the crankcase into the airbox.

[Pete in PA]

Once you've fixed a vacuum operated petcock it's easier to understand.

Know that when that diaphram goes bad, gas and air can go where/when it shouldn't.

Deffinately keep the airbox and keep the crankcase venting into it.