Modern Vespa

My 2007 LX150 died the other day and wouldn't start. I noticed some fuel beneath the carburetor and investigated. When I lifted the carburetor to look underneath, there was what appears to be a drain hose that had broken off. I cut a bit of the old hose off to make a clean end, reattached it, and was able to get the engine running again. The hose being detached from the drain appears to have been the problem. I'm stoked that it was relatively easy to get the bike going again within a few minutes, but there is something I'm not fully understanding.

This hose appears to be routed down the side of the engine toward the ground, and...is connected to nothing. This makes sense to me if it is a drain/overflow. What I'm not clear on is why the engine won't run without this hose attached. Can anyone explain why a short length of hose make such a difference?

Hose is in fact a drain for float bowl, routes fuel to the ground if float valve should stick open. Non-start condition was probably due to stuck float as evidenced by puddle of fuel. Fix was in manipulating carb you jarred stuck float loose. Drain hose could be completely absent and engine would run. If issue recurs may need a carb clean and possibly a new float needle.

Ah, that makes more sense than a short piece of hose to nowhere causing the problem. I'll take a look at the carb when I have time and see what's causing the float to stick.

Thanks!