Carb Vent tubes

[mista_max]

Hi ,

I was just wondering if the vent tubes on the carbs are necessary.

Max

 

[maleko89]

Yes, unless you have stage 7.

 

[one2dmax]

Even with a stage seven it's best to leave the hoses on and zip tie them up to the frame in the same general area.

 

[lethal dose]

Bump. My bike came without the hoses that go from the elbows on the carbs to the airbox. It runs fine. Is there a logical reason that I should put them on?

 

[thor_eyerdhal]

Atmospheric pressure goes into the carb bowls thru it, length doen't change the pressure value.
In case of stuck needle, the hose length delay the gas spill over the engine.

 

[Dragmaxster]

Bump. My bike came without the hoses that go from the elbows on the carbs to the airbox. It runs fine. Is there a logical reason that I should put them on?

I have an extra pair.

 

[lethal dose]

I guess what I'm getting at is the fact that my bike runs fine without. Are they just there to keep fuel at bay and not dump on the motor?

 

[D-Max2012]

Not taking away anything from Nicolas Cage, but if you dont want to be like this,

try your best to keep raw fuel off a hot engine.. :rofl_200:

 

[Traumahawk]

I guess what I'm getting at is the fact that my bike runs fine without. Are they just there to keep fuel at bay and not dump on the motor?

I was always under the impression that they are strictly vent hoses....and have nothing to do with keeping fuel off of the engine. In the throat of the carb you can have negative pressure....but the rest of the carb needs to be at normal atmospheric pressure to be able to pull fuel out.

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[Traumahawk]

Here is from a keihin CV website

The vent holes are connected by internal passageway to holes in the top of the bowl chamber. Venting keeps the inside of the float chamber from developing a vacuum which would cause the floats to function erratically.

http://www.wgcarbs.com/index.php/us...nt-component/article-categories/91-cv-connect

All CV carbs basically operate the same way. BUT....Some CV34 assemblies have black plastic tees connected between the 1 and 2 carburetors and 3 and 4. These tees serve the same function as the internal vent passageways connect to these instead of the holes on the venturi edge. In either case, the vents must remain clear and unobstructed. On some bikes, if there are vent tees, these will be connected to hoses which route to the airbox or may route over the swingarm. The main idea is that they not be obstructed or pinched. If your bike doesn't have the tees, don't worry about venting. The point of the hoses is to route gasoline away from a hot engine in the event the bike overturns. If it routes into the airbox, you will very likely need to replace your filter element if the bike overturns as it will be gas-fouled.

 

[Dragmaxster]

If you pinch one of these hoses while replacing your airbox you are in a world of hell.:bang head:

 

[lethal dose]

How so?

 

[Dragmaxster]

How so?

They run from the tubes to the airbox and go between the airbox and frame- if not in the right position they can get pinched --- it will greatly disturb the carbs airflow.
Just follow the manuals routing.

 

[one2dmax]

They do have an affect on the carbs for many people and it's simply better most of the time to have them. if it's running well without them and no cruise surges or other poor operation then you can leave them be. They won't hurt anything other then they could leak out fuel more readily under hard acceleration since the fuel has a lot less travel to go before it could spill out.

Sean

 

[Dragmaxster]

They do have an affect on the carbs for many people and it's simply better most of the time to have them. if it's running well without them and no cruise surges or other poor operation then you can leave them be. They won't hurt anything other then they could leak out fuel more readily under hard acceleration since the fuel has a lot less travel to go before it could spill out.

Sean

+1 Also leaves a mess on the paint with discoloration.:bang head:

 

[lethal dose]

Is there any risk of dust getting into the hoses (or elbows if hoses aren't present) and mucking up the carbs? I understand the function is to vent, but is it an active vent or more of an overflow?

 

[Traumahawk]

I would say that it's more of a vent. It's only an overflow if your on your side....and hopefully you don't spend much time there. I would say that the chance of picking up dust....etc....is lessened due to the vents facing backward....IE the rear of the bike.

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[lethal dose]

But with the hoses, they face fwd.

 

[Traumahawk]

But with the hoses, they face fwd.

Yes.....but they have they metal ends on them when they attach to the air box. When the tube are off.....the vents on the carbs face rearward.

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[lethal dose]

Right, but my "t" and metal brackets are non existent... so I guess it'd be best to leave the hoses off?