Quick "ID these carb parts" question

[raub]

in the following picture,

What is the passage marked in blue for? Where does it go?

Also, can I operate the throttle jets (or whatever the two pipes that are controlled by the throttle lever) while carbs are headless like these? What about the jets on the venturis?

The hose marked in blue here,

is it how the front carb's throttle jet gets fuel?

Apologies for the large pictures. I have not ridden my Vision in years and can't remember most of how the carb goes. And the manual was confusing me a bit...

[QBS]

Top picture, circled in red= accelerator pump nozzle
Lower picture, circled in red = fuel supply line for one of the accelerator pump nozzles.

The accelerator pump itself is attached to one of the carbs and feeds the accelerator pump nozzle on the other carb via this fuel line.  I'm not sure if you need to have the carb tops on to operate the accelerator pump.

[AdvRich]

Hi Raub, those look to be '82 carbs which are a bit different than '83's I am more familiar with. The area in blue is not on the '83's so I can't offer much more than they are most likely for passage of air or vacuum in connection with fuel uptake within the carb body. The holes may correspond to the bottom of the airhorn (carb top) even going to one of the air jets. The accelerator nozzles can be squirted with the carb tops off, you'll need fuel in the float bowls though and the passages (which are small and have a check ball and screen) need to be varnish/gum free to flow as you rotate the throttle plates.

Curious if you are trying to figure out how to get the fuel flowing to fire this Viz off or just having metering problems with regular operation? Hope this is of help. Rich

[Cdnlouie]

Blue circle is fuel bowl vent, the front one connects to the exterior filter and the rear one draws air from inside the venturi.

Don't get lost in there!  ::)

[raub]

AdvRico, right now I do not think I am getting any fuel out of the carbs. So I am trying to find out why. First, I was thinking on making sure the accelerator nozzles do work. And that is why I would like to see if I can test them with the carbs headless.

If I am not mistaken, the check ball is kinda right under the part of those accelerator nozzles that is pressed into the carb bodies, right?

Cdnlouie, if those are just vents, I should not need them for as long as I have fuel in the bowls if I just want to start the bike, right?

About the  accelerator pump, if I disconnect the hose to the front carb, have fuel in the bowls, and crank the throttle lever, I should see fuel coming out of the hose.

[Rikugun]

I would think the vents being clear and open is just as important as any other jet or passageway. You need atmospheric pressure above the fuel in the bowl for the carbs to operate. We think of manifold pressure as "sucking" the fuel into the venturi but without atmospheric pushing down on the resevoir of fuel it's not a happenin' thing!  :)

[AdvRich]

AdvRico, right now I do not think I am getting any fuel out of the carbs. So I am trying to find out why. First, I was thinking on making sure the accelerator nozzles do work. And that is why I would like to see if I can test them with the carbs headless.

The accelerator pump has to be problem free (not clogged up and good diaphragm operation) and the uptake port in the bottom of the float bowl and the passage to the pump needs to be unobstructed to get a squirt through the hose. I'll just ad that the Viz carbs need to be fully cleaned, inspected, and float levels set and then synched to get the std baseline of operation from them, anything short of that will only add to less performance and more head scratching when other engine system problems get added to the mix.

You mention "not getting any fuel out of the carbs." Going back a bit in the line of fuel delivery, does the petcock flow in the Prime position? and flow under vacuum when on Res and On? Is the fuel pump fully performing?
 

If I am not mistaken, the check ball is kinda right under the part of those accelerator nozzles that is pressed into the carb bodies, right?

Yes.

[Night Vision]

IIRC; behind the accelerator pump diaphragm, in the "well area", there is also a little check ball that could be gummed up... if the nozzles are clean and they aren't getting fuel, that might be the problem...

besides the float bowls having gas in them and accelerator nozzles squirting when working correctly, you won't "see" if the carbs are getting fuel... as said above.. these are downdraft carbs and the fuel is "sucked" into the intake manifolds when intake valves open and the pistons draw down   

[raub]

Let me add a few more pictures. First we can see my test fuel tank (Battery cables since I am using a car battery placed away from bike to provide power):

Fuel level on the test fuel tank only decreases while cranking the motorcycle. I also checked the fuel level at the bowls:

It seems to make me think the floats are doing their job.

What can I test on the bench? I do have another set (I should have a third one somewhere...) of carbs I would not mind cleaning and making sure it works before swapping back into bike. But, anything I can do with carbs in bike...

[Coil Coyle]

Don't forget that when you used a more powerful source of electricity it is possible to overheat the starter motor if you crank to long without a cooling break.
Crank some, cool some.

$0.02
;)
Coil

[raub]

Makes sense. I pretend it is an aircraft: starter on for 10s, starter off for 30s

[Cdnlouie]

Raub... ??? I can't help but ask, what are your trying to do with the carbs?  Are you just checking them out? Are you having trouble getting it to start? Or does it run a bit, but not so well? If the bike is not running then you may well need a complete carburetor tear down, cleaning and who knows what else corrected in their setup.

I don't think I can remember in recent history taking a Vision carb apart and not finding something screwed up. It's amazing what 25 years of people learning to take apart Vision carbs can actually do. If these have not been run in recent history, they will no doubt minimally need all the jets removed and cleaned in order to have a chance of starting the bike.

[Lucky]

your float level is WAY low.. it should be close to the gasket in hight.  see the service manual for the correct hight.

also, get that pony tank high up in the air. gravity will help a lot. the bikes fuel pump only makes a difference when the tank is low on fuel...

[raub]

Thanks for the info, Lucy. I checked with my caliper on my other carb set,

and I am indeed way below the 20mm mark.   :o

When I had my pony tank at the original height (hint: note the length of the hose), I was leaking fuel at the plastic drain ports. Needle valves bad/dirty?

[Lucky]

yup and/or the o-rings on the drain screws are bad...

[Lucky]

& Who's "Lucy"??  did i pull the football away from you Charlie Brown? lol

[Ken Williams]

A less than robust fuel pump can keep the carbs from filling properly.  Recommend you check float levels with fuel supply above the carbs, not flowing through the fuel pump.  Your on bike test may indicate a bad pump instead of really low float levels.