What to do with vent port on CA carb

[kpke]

The brass vent port on the right side carb on California specific carbs had a pipe that ran somewhere??? Either to the smog cannister mounted by the radiator shroud or to the bottom of the fuel tank where there is another vent. I'll be using these carbs on my current build.

What do you do with this vent port when not using it? Can it be capped off or does it need to keep "venting"?





Found an old photo but still don't know where the other end terminates.

[75RD350rider]

I have no idea Ken. But if it was me I would just let it vent only because plugging it might cause something detrimental. I will do some research.

[speedfrk]

I capped it off on my CA bike. It had a Dynojet kit in it and I think it is supposed to be capped or it will run very lean on that cyl.

[kpke]

Thanks speedfrk. I appreciate the reply. I have installed Dynojet needles also.

[brrrappp]

On the non-ca carb this is not drilled through. If you have removed the rest of the smog junk and have expansion chambers then you likely have jetting in line with the non-ca bikes. If that is true, then blocking it off is probably the correct answer.

[75RD350rider]

Glad you fellows know more about this than me. My knowledge of the smog stuff is nearly non-existent. My RZs either don't have it or it was taken off.

[brrrappp]

Glad you fellows know more about this than me. My knowledge of the smog stuff is nearly non-existent. My RZs either don't have it or it was taken off.

I have a NON-CA model. So the following is just a guess<<- I looked at the parts schematic and I think that vent may have been connected to the carbon canister to draw gas fumes from the fuel tank into the carbon canister. The carbon canister would likely have a check valve that would limit vacuum - otherwise it would create too much vacuum in the fuel tank.
So - again just a guess - the air flow to that carb vent would be limited. Logically, if your main jet, needle and pilot are at 49 state specs, if you plug the vent you should be safe.

[kpke]

Thanks brrrappp. These CA NC2 models have the carb vent, the cannister, the vent on the bottom of the fuel tank, and a "special" fuel tank cap. The fuel tank has less capacity as a result of venting. I believe it is all connected as you said. I will start out with capping it off which I believe is the correct answer. I was hoping to hear from kobra as his NC2 restomod build used these carbs.

[Smoker]

I don't think it's a vent port. I think it's a vacuum port.

Should be connected to a vacuum actuated petcock. If the petcock has a "PRIME" position, it's a vacuum actuated type. If the petcock says "On/Off/Reserve", no vacuum connection is required. Pretty sure on the CA bike, the vacuum port is connected to the emissions control equipment. The vacuum port must be connected the way it was originally intended to operate, or it must be capped with a vacuum plug.

[speedfrk]

Only the CA bikes have this port. If you have taken off the smog stuff, it needs to be capped.

[kpke]

This port will be capped off. kobra PM'd back and said that he capped them off also. That's two real life situations. Thanks again for the replies. Smoker, this is not the vacuum port for the petcock. It is California special smog stuff.