82 CB650SC air filter housing hose?

[Munkey]

As long as you have the copper and aluminum tubes in place, the only other port left would be the one with the rubber T's that just vent to the airbox. Or like it was on my bike since the hose to the airbox was missing, just vents to the atmosphere.

[Beetlegeuce]

I'm not concerned with the connection at the airbox itself...its the connection at the carb being open that concerns me.

I think I see where the hoses connect at the carbs (maybe?)...small port on the side that appears to have had something on it at some point (tip is cleaner than the rest). 



Does that look like where the "missing" hose(s) would connect?  Is this going to be an open vacuum port?

[Munkey]

Is is missing the little rubber T's that I've been taking about. They are not vacuum ports, just vents. I guess the only real issue with not having them vented to the airbox is the possibility of dirt getting in the carbs through them. I ran mine for years with just the T's and no hose on them and it ran fine had no problems.

[Beetlegeuce]

Yep after looking a little closer I see that these are vents for the float bowls.  Shouldn't be difficult to find a "T" that'll fit on there.

Thanks for all the help!

Bill

[Bumblebee]

Yep after looking a little closer I see that these are vents for the float bowls.  Shouldn't be difficult to find a "T" that'll fit on there.

The air T connectors are $25-35 a pop. It has to be an airtight fit. The T hose must be able to exist in a high temperature fuel saturated environment (IOW, no cheap non fuel rubber) The only way to replace them is to separate the carburetors from the rack. Don't go cheap on yourself, replace both at the same time. It's a high failure rate part. It screws up performance and mileage. It's my #1  on the VB44 carburetor.

Get a good manual (preferably the official honda shop manual), don't adlib anything and see my two threads on throttle plate bench sync and choke spring linkage for this carburetor.

[Beetlegeuce]

I don't understand something here...

Ok so these are just bowl vents, straightforward enough.  Each carb has has two bowl vents, one on each side, both vents open into the float bowl.  On the outer two carbs the outer vent port of each is plugged.  The inner two carbs have just a simple hose connecting to two "inner" vent ports of those two carbs.  The outer ports of the inner two carbs connect to the inner ports of the outer two carbs (confused yet?  ), providing a vent path for all 4 carbs.  My question is...why "T" off of the connection between the outer/inner carbs, which has VERY little room between them.  Why not "T" off of the two inner carbs, with just a simple hose between the outer/inner carb pairs?  The 4 vents are still all connected together, and that would make the connection up to the airbox hose (the original "mystery" hose in my first posting) SO much easier.   

Bill

[Bumblebee]

Other designs are likely different however for the 82 VB44A/C carburetors:
First off, there's not a lot of room between #2/#3 to run an extra hose out with all the control hardware and main fuel line there. There is a lot of hardware packed into a small space with the structural bar beneath the tank where it is.
Second, flip the carbs over and remove the float bowls and take a look at the plumbing inside to see exactly where those hoses connect and how they continue and open up into the float chambers. There are two independent vents into the top of the #2 and #3 float chambers. The second vent hole goes to the #1 and #4 carbs respectively without a direct single connection across all 4 carburetors. IOW, air goes from say the #1/#2 T connector into the #2 carb float chamber, then across inside the #2 chamber then into the plumbing going to #3. Make sense?

Now think about air pressure.

#2/#3 cross vent hose stabilizes air pressure between those two chambers.
#1/#2 T connector stabilizes the pressure between those two float chambers and the same happens between #3/#4.

When riding, fuel sloshes around in the float chambers. At high fuel flow rates with the motion induced sloshing, the floats open more often and the chambers are more full than when the bike is running on the centerstand. When a chamber is too full of fuel with the fuel sloshing, the air vent path across that specific chamber closes off for a moment which causes an air pressure imbalance to the next chamber over in either direction depending on which chamber is too full.

When there is lower pressure above the fuel in any given float chamber for a generic anything carburetor, the fuel flow rate is reduced into that venturi thus the mixture goes lean which causes a power loss. (That is why all float chambers must have a vent to atmosphere instead of being sealed off from the outside world) Then when the fuel finally drops enough for the valve to open there's a sudden rich condition for a moment. In the meantime, the other running cylinders are continuing to drive all 4 intakes even though one cylinder has lost power. Add in the vacuum piston chamber on top and that piston will start moving up and down as the total vacuum starts becoming unstable. Repeat quick enough and there are multiple power surges that cause the total fuel consumption rate to be higher than normal. The further open the throttle is with a pressure imbalance, the worse the situation becomes as the vacuum pistons move up and down significantly altering the vacuum thus fuel flow through the venturi.

To fix this problem, the cross over hose off both T connectors are plugged into each other at the air box T connector. The air box hose is nothing more than a fixed stable near atmospheric air pressure supply equal to the air pressure entering the carburetor throat. The cross over hoses stabilize the pressure between #1 and #4 even if #2 or #3 are temporarily closed off. Thus the air pressure on top of the fuel remains constant across all 4 chambers therefore the fuel flow rates for each carburetor remain in sync.

Remove the T connector hoses completely or put a crack in one and the airflow rate/pressure starts to vary between the chambers. That situation is bike dependent. I've heard some of the 650 nighthawks are ok with no hose or cracked hoses while others have the same problem mine does. My standard 650 doesn't have all the extra plastic that the nighthawk has so I get a much more pronounced turbulent air flow in the vicinity of the carburetors. When those hoses crack or come off on mine, the turbulence is sufficient to cause pressure imbalances between the right and left sides of the carb assembly. That causes loads of grief to the point that it won't run more than 45mph and mileage goes from 57mpg to 36mpg.

It's late at night and I've been up for about 2 days straight so I hope that makes sense.

[Beetlegeuce]

Yeah it does make sense.  Thought about that a little more myself last night...like why would it be set up specifically like that and just figured it was for vent pressure balancing.