Modern Vespa

problem with a modern carb'd Vespa LX50 not starting. Was running fine, then started bogging, now won't start at all. Motor turns over.

• spark- check

• battery- check

• fuel tap works when I suck on the vaccuum hose but doesn't draw fuel when hooked up to intake manifold.

• carb inspection reveals that the vacuum valve is NOT stuck and is all the way down as it should. It moves up and down freely. Nothing really jumps out on the carb as being "off"



removed the carb. No obvious tears or leaks in the intake manifold or the rubber hose between carb and airbox



so...... where do I go from here? Clearly there seems to be an air leak which is resulting in no fuel being delivered. As mentioned the fuel tap work fine when I manually suck on the vaccum line. Also- when we removed the carb, I put my hand over the intake end (where is attaches to carb) and turned over the starter on the bike. Fuel flows fine with the intake blocked off by my hand , so the leak isn't involving the manifold itself. Seems to be coming from carb. Thoughts?

The intake manifold can crack/perish resulting in air leak between carb and reed valve. That may be the issue.