Carb face bowl vent leak

[The Wang]

I just redid the float seat because it was torn and gas was flowing into the bowl, up the jet and flooding the engine, now after mounting and connecting the carbs to the tank It gushes fuel out of the top right bowl vent on the face of the left carb.

Anyone know what could cause this? I was guessing a blockage somewhere or maybe a missing part, after rebuilding parts of these carbs I noticed parts that were worn from someone taking them apart, considering I bought my xs400 from someone who'd left the project im guessing they took it apart and lost something.

I took an endoscope before posting this, leaving them mounted, and can see the fuel coming up from the bowl

 

[tstidham]

Check the float heights would be my first step. And also check the petcock is shutting off fuel as well.

 

[The Wang]

Check the float heights would be my first step. And also check the petcock is shutting off fuel as well.

My petcock doesn't shut the fuel off, at least not in my experience. I've had to use a line pincher or vice grips to cut the flow, I didn't think that mattered, what bothers me more is that I sat the carbs with the tank elevated on my workbench overnight before mounting them and they didn't leak, as soon as I mounted them the leaking started

 

[OleDoc2]

Could also be dirty float needle

 

[The Wang]

Could also be dirty float needle

Brand new needles, checked floats, new jet.

Could it be a diaphragm needle issue?

 

[OleDoc2]

Brand new needles, checked floats, new jet.

Could it be a diaphragm needle issue?

Or float height

 

[tstidham]

Technically it shouldn't matter as the float level should exert enough force to seal the needle and seat, however if the level is wrong it will leak fuel, even when running.

 

[The Wang]

Technically it shouldn't matter as the float level should exert enough force to seal the needle and seat, however if the level is wrong it will leak fuel, even when running.

What's the correct way of gauging the correct float level, as I mentioned before I tested the carb that's leaking with the bowl off to make sure the float would seat the needle, and I checked the float depth before, I think it was 24 or 25mm but I could be wrong it's been around half a year since I last messed with the carbs

 

[tstidham]

I have a 78 and used 26mm, other years have spec'd 32mm (or maybe that's the dohc bikes). Many forum members prefer the tubing method of 1 mm below carb bowl to carb body line. I also replaced my vacuum petcock with a mechanical one so I had a confirmed closed fuel supply.

 

[avemachina]

I'm a tubing method kinda girl myself--I had brass floats to 26mm, then rubber floats to 24mm-ish. For SOHC bikes, it's 3mm +/-1mm below the carb body per the Haynes. The tubing check is helpful because it actually shows how much fuel is in there, not how much should be in there. You only need maybe 6in/15cm of 1/4" tubing to hook to the bowl outlet, so it's not hard to do.

You can also rough the measurements in with the carbs off--set one float to like, 22mm, and the other to 26mm, measure the fuel difference between the two, and dial in what the actual height should be for you to get to 3mm below the body (that's how I landed at 24mm).

 

[OleDoc2]

Technically it shouldn't matter as the float level should exert enough force to seal the needle and seat, however if the level is wrong it will leak fuel, even when running.

Dirt can also get between the needle and seat, causing it to leak. It's a very common issue with Kawasaki 750 Vulcans