KZ400 Single Carb - NEED HELP! (PWK35)

Okay... I am baffled. I was using the CV style carbs, so this flat slide is new to me. My petcock is not vacuum operation, and either is the carb.

When I turn the petcock ON, the fuel line fills, and the bike runs fine. However once the carb uses up whatever is in the float bowls, and whatever is in the fuel line, fuel STOPS flowing from the petcock. So the bike essentially run out of gas. If I stop, turn the petcock off, and then back on, it starts flowing again and does the same thing over again.

WHY does the fuel stop flowing? Is this a back pressure thing? How do I fix it!?

Try it with the fuel cap open, just into a container, check the flow. It may have a blocked tank vent which is in the cap.

That was suggested before... Would that make sense though considering when I turn the fuel off and then on it flows freely again?

Plus, if its not connected to the carb it flows freely. Gas cap on or off.

An in-line, paper, fuel filter can cause weird symptoms like that. If you have one, you may want to get a scintered filter or a metal screen filter.

your petcock has to nipples, one for output and one for vaccum signal to open the diaphram to flow fuel. make sure the vac nipple is getting good vac. you can suck on it and watch it run if you need to. next if thats all proper check that the floats still dropping to allow the needle seat to open. from what it sounds your getting the prime amount from turning the petcock lever and thats it. your vac signal has to be hooked up and if not you need a gravity petcock. good luck ill keep checking back to try and help

No vacuum. Aftermarket petcock. No flow when connected to carb.

Here is a link to the Keihin PWK 35 parts breakdown. www.jetsrus.com/carburetor/carb_keihin_P...oded_view_parts.html
Maybe open the drain screw, and watch the flow into a container. The hinge on the float may be sticking, or the float adjustment could be wrong. There is both a fuel height and a float drop adjustment. Basically the drop adjustment is so it can open the valve fully without the float contacting the bottom of the bowl. You can check the height with a clear piece of tubing held alongside the bowl. I don't see any inlet filter screen in the breakdown, but there could be one, or something else causing the restriction. With the bowl off you can operate the float with your finger and watch the flow.
Have you had the bowl off? Checked the fuel height? Or anything yet?

Maybe the float valve is just sticking for some reason? Try giving a hearty tap to the carb bowl with a screwdriver handle or something similar to see if that opens it back up when it gets stuck. If that works, I'd just give it a thorough cleaning and try again.

I've opened up the carb and everything appears to be operating just fine. However I am not sure what the float height is suppose to be. Have had a hard time finding that info online.

About 3mm below the gasket surface, fuel level checked with a clear piece of tubing attached to the drain, drain open petcock on, route the tube up along the side of the carb for a sight gauge.

How about the carb bowl vent? The bowl must have a clear vent to allow fuel in.