Modern Vespa

On a Vespa LX 50 is it normal to have fuel in the vacuum line to the fuel tap?

The bike is a 2005 with carburetor.

I'm having stalling/flooding issues and wonder if this could be contributing to the problem. I've already replaced the tap once and was trouble free until recently when I started noticing fuel in the vacuum line.

I have a Mallossi 75cc kit with performance cam installed but otherwise stock. Ran that way trouble free for years. I wonder if the larger piston creates too much suction for the fuel tap causing it to fail.

I unplugged the auto choke and replaced the fuel tap last year and was problem free until now. Now intermittently it will stall out and not restart. If I leave it overnight it will usually start up again.

Any ideas?

Sounds to me like a leak in the diaphragm in the tap.

There should be no fuel in the vacuum line.