Fuel leak from carb

I noticed a fuel leak about an hour ago from my carb, it was comming from the overflow tube on the bottom. This happened right after I replaced the fuel hose, the new hose had a slightly smaller diamater than the last hose if that is of any significance. I put the old hose back on but it didn't make a difference so I took the bottom bit off the carb but I couldn't see any debris inside so I put it back together and the problem went away. What I want to know is why would a new fuel hose cause this? I've dissconnected the old hose plenty of times and this has never happened before.