Carb Questions

[Dan in Grand Rapids]

Hello Everyone,

I took my carbs off for the first time and I thought they had never been out before, but it looks like they have. The air/fuel screws did not have the plug over them and they were set at almost 4 full turns out. I can't believe I rode it 55,000 miles like this. Anyways, there are two nipples on the carb bank that are not connected to anything and that seems strange to me. They look like something should be connected otherwise contaminants would enter the carbs. What do these go to? I appreciate your help.

[DC Concours]

Those look like vent ports. There should be clear hoses connected to them that then attach to the side of your frame.

[Dan in Grand Rapids]

Thanks for the reply. That makes sense and I will have to find some clear tubing to add to them.

[K-woppa]

Yes, carburetor float bowl vents. You could also turn them so they face down. They fit into the carb bodies with orings and usually turn fairly easily.

[Jim __]

Not sure why you would turn the nipples to face down.  Is there an advantage to this?  The manual shows the routing of the plastic tubes to the frame with the nipples facing up.

[jettawreck]

I see Dan is in one of the "other" Grand Rapids'.
Hi, Dan!
Havin fun with the Connie carbs, huh?

[Dan in Grand Rapids]

Thanks for the replies guys. I am taking a break from the carbs right now. Every time I adjust the valves I bump the thermostat and start a coolant leak. It usually bumps back into place and the leaks stop, but not this time. I just ordered a new seal for that and new coolant log o-rings. Once those go in then I will be back to carbs. The "other" Grand Rapids? Iowa?

[Mettler1]

Thanks for the replies guys. I am taking a break from the carbs right now. Every time I adjust the valves I bump the thermostat and start a coolant leak. It usually bumps back into place and the leaks stop, but not this time. I just ordered a new seal for that and new coolant log o-rings. Once those go in then I will be back to carbs. The "other" Grand Rapids? Iowa?

   Minnesota?

[K-woppa]

Not sure why you would turn the nipples to face down.  Is there an advantage to this?  The manual shows the routing of the plastic tubes to the frame with the nipples facing up.

I should have said, you can turn them down and leave the hoses off.

[jettawreck]

   Minnesota?

Correct.
And there is another one in Manitoba, probably among others.
Often stuff headed to the GR in MN has taken a detour by way of GR MI.
Several years ago coming home from Florida the airline was trying to get us home after an overbooking and the counter agent had us routed to GR MI because she wasn't paying attention.

[Stasch]

I should have said, you can turn them down and leave the hoses off.

Any vacuum exposure to these vents due to cross winds or back draft can cause issues with how the carbs let the bike run. 

If it happened, even sporadically with the perfect storm of conditions, you would go crazy trying to figure it out.  Even with everything else set up 100% right this scenario could cause you grief like an invisible gremlin.

Not saying they'll have much different air / vacuum exposure pointing down between the carbs, but I would equip them like the factory did with tubes routed up and along the frame towards the back, behind the side covers

It'll cost about $.50 in clear tubing and a couple of zip ties to do it right and you won't have to worry about it. 

My $.02

[Dan in Grand Rapids]

Thanks for the replies guys. I will look into some clear tubing for the vents.

[MAN OF BLUES]

I should have said, you can turn them down and leave the hoses off.

that doesn't work, and will cause problems. Install the hoses, and route them as they were installed at the factory.

Leaving them open, or turning them down without hoses, will actually cause a vacume and suck fuel / vapors out of the bowl, and also allow moisture to contaminate the fuel in the bowls. The vents are to allow a passage to atmosphere, to allow fuel to flow into the otherwise sealed bowl, when the floats drop and the fuel flows in.

route them up like shown here

[K-woppa]

that doesn't work, and will cause problems. Install the hoses, and route them as they were installed at the factory.

Leaving them open, or turning them down without hoses, will actually cause a vacume and suck fuel / vapors out of the bowl, and also allow moisture to contaminate the fuel in the bowls. The vents are to allow a passage to atmosphere, to allow fuel to flow into the otherwise sealed bowl, when the floats drop and the fuel flows in.

The op has already stated that he will be fitting hoses to the nipples. Fine and dandy. However, I disagree with you. The vents are not only to allow fuel to flow into the bowls, but also to exert atmospheric pressure on the fuel in the bowls. The differential between this and the venturi pressure is what forces the fuel through the passageways, into the carburetor throat. If enough wind blows across the ends of the nipples, yes, a vacuum can be induced. In their isolated position between the carburetors, though, I don't see how enough airflow will develop to affect their operation, never mind "suck the fuel" out of the float bowls. I had the vent nippple turned down on an ex500 for years, no problems, and it's much more out in the open than on the Connie. In fact, the stock location of the clear vent tube on the ex500 has been known to cause this exact problem under certain conditions, so among owners of that particular bike it's accepted practice to remove the hose and turn the nipple down. I don't see any such problem with the Connie, though, since the hoses are tucked away behind the side covers.

[MAN OF BLUES]

The op has already stated that he will be fitting hoses to the nipples. Fine and dandy. However, I disagree with you. The vents are not only to allow fuel to flow into the bowls, but also to exert atmospheric pressure on the fuel in the bowls. The differential between this and the venturi pressure is what forces the fuel through the passageways, into the carburetor throat. If enough wind blows across the ends of the nipples, yes, a vacuum can be induced. In their isolated position between the carburetors, though, I don't see how enough airflow will develop to affect their operation, never mind "suck the fuel" out of the float bowls. I had the vent nippple turned down on an ex500 for years, no problems, and it's much more out in the open than on the Connie. In fact, the stock location of the clear vent tube on the ex500 has been known to cause this exact problem under certain conditions, so among owners of that particular bike it's accepted practice to remove the hose and turn the nipple down. I don't see any such problem with the Connie, though, since the hoses are tucked away behind the side covers.

well, I guess we can agree to disagree.
this ain't an EX500. I have no clue about what works or doesn't on them.

I think I have seen every permutation of what someone deemed as "ok" as far as carbs on a ZG goes, over the last 13 years... and have fixed the ones, that people thought were "ok"/ but they had issues....
short of Bubba Steve, I don't think anyone around knows more about ZG/Kehein combo issues, and even Steve will sit and talk with me about mysteries on these carbs. We just live them. Plain and simple.
with that said, and not trying to be a smartazz, I'll just ask you to go out, pull those hoses off your ZG, turn the fittings as close as you can to upside down, and ride it.
Then come back, after going thru 2 tanks of fuel, (approx 500 miles) and tell me it ran no different, or even better...than it did with the hoses attached, and correctly routed... oh, and make sure out of that 500 miles, at least 100 of them was driven on a freeway at 70mph, drinking from a firehose in a torrential down pour.
 

Thanks for your input.
the hoses need to be in place.
and routed up and behind the side covers.
and yes, when in position they are located up high under the side panels, but if the hoses are removed, the side covers act as a funnel' and introduce turbulent air all around the carbs, and rear of the head, that is why when a carb clamp is loose, it it VERY evident there is a problem.. lots of air in there, swirling...

telling someone to do what you "think" is ok, ain't gonna cut it.
sorry.

[T Cro ®]

As the OP question has been answered it is now closed.....