Modern Vespa

I ordered a new vacuum controlled fuel petcock, installed it, tested it by sucking on the vacuum line to make sure fuel came out, it did. Hooked fuel line up to the carburetor, sucked on it again for a few seconds to fill the bowl up, scooter wouldn't start. Pulled the fuel line back off, sucked on the vacuum line again, I can't get fuel to come out now.
I feel the diaphragm moving when I suck on it. Any suggestions? I have another one on order.

Thanks

If you hear the diaphragm shift when applying vacuum to the petcock, it should flow fuel readily.

It shouldn't take much vacuum to open the petcock.

You might have a bum tap.

That's what I thought, we'll find out tomorrow.
Will give update.

If you have a mity vac, or similar, you might try that. I could take a bit more suction power.

Replace your black fuel line with a transparent Tygon line and you'll be quite surprised by what goes on (and doesn't go on) in there. Fuel doesn't just gush into an empty line sealed off at one end, displacing the air, when the petcock is opened by vacuum. The needle valve in the carb has to open to let the fuel in, or you have to disconnect the line at the carb and turn the engine over a few times to let the fuel flow down the line, then reattach it.

Or, don't worry about it. If a little oral suction on the vacuum valve gets the fuel flowing out of the petcock, it's probably totally fine. If the carb is empty, the fuel will get to where it needs to be when it has a path to get there, though it might take a few cranks/kickstarts to get it going.

Fuel flowed one time when I put vacuum on it. Never could get it to flow again.
When I put the new fuel tap on, I'm going to fill the float bowl up with a syringe so there is no lag time to get fuel in the carb.

Who would have thought to test a brand new piece of hose to see a fuel would go through it. All of this turned out to be a clog in a brand new piece of hose. Unbelievable!

After further investigation of the piece of hose, there is a big solid bulge in the end of one section of hose. Took one of my picks and pushed through it no problem. Appears to just be part of the hose wasn't formed properly.

Wow! Where did that hose come from? It has ONE JOB.

Bought it off Amazon, nice silicone hose.