What is this hole for on the side of the carb?

Mucci · Post by **Mucci** » Fri May 08, 2015 5:10 pm

I'm tuning my CA95 after a rebuild. I feel like I've dialed the jetting in really well at this point. The issue is the idle will either run really high or bog out whenever it feels like it.

While the idle was running off I moved around the carb with an open can of propane to find a possible air leak - which I did. Whenever I put the propane right up to this tiny port hole in the right side of the carb, the idle will immediately come back down and gas will trickle out of the over flow line. As soon as I remove the propane it runs back up again.

What is this port hole for and how do I fix this issue?

Hahnda · Post by **Hahnda** » Fri May 08, 2015 5:49 pm

I believe that is the bowl vent.

Have you checked your float height?

Mucci · Post by **Mucci** » Sat May 09, 2015 9:40 am

Hahnda wrote:I believe that is the bowl vent.

Have you checked your float height?

Hmmm, can float issues cause a varying idle like this? I had a pin hole leak in the brass floats that I soldered up. Maybe it's still causing issues. I'll pull them to check if any fuel got in and reset them.

Waveblaster · Post by **Waveblaster** » Sat May 09, 2015 10:55 pm

I was looking at my c92 carbies which are pretty much the same. They have a brass peg in that hole . Underneath the peg there is tiny hole . Perhaps the peg missing is contributing to the air at idle particularly if the float height is low.

Mucci · Post by **Mucci** » Sun May 10, 2015 10:15 am

Waveblaster wrote:I was looking at my c92 carbies which are pretty much the same. They have a brass peg in that hole . Underneath the peg there is tiny hole . Perhaps the peg missing is contributing to the air at idle particularly if the float height is low.

Should that vent hole be sucking air in at idle? Does anyone know the purpose of the vent hole / when it's supposed to be in use?

Hahnda · Post by **Hahnda** » Sun May 10, 2015 10:22 am

The vent hole provides a vent to allow the fuel to be drawn through the jets. Looking at other CA95 carbs it appears that your vent is correct. Without the vent it would be like sucking through a straw from a sealed container.

Without looking at the carb I would say that your fuel level in the bowl could be to low and one of your jets is not in the fuel. When you stick the propane near the vent it is drawn in and through that jet.

Mucci · Post by **Mucci** » Tue May 12, 2015 9:35 pm

Hahnda wrote:The vent hole provides a vent to allow the fuel to be drawn through the jets. Looking at other CA95 carbs it appears that your vent is correct. Without the vent it would be like sucking through a straw from a sealed container.

Without looking at the carb I would say that your fuel level in the bowl could be to low and one of your jets is not in the fuel. When you stick the propane near the vent it is drawn in and through that jet.

Well although I thought I remembered setting the float height after repairing the floats, at this point I'm going to say it looks like I forgot. The floats were just resting on the inner surface. That along with a couple jet changes got her running real smooth. Thanks for the help!