Small Engines (Lawn Mowers, etc.): Craftsman LT2000 w/ Honda GXV530 Engine, craftsman lt2000, vacuum line

Question
When I started my riding mower this season, I noticed that it ran rough, backfired and had a strong fuel smell.  I replaced the spark plugs and the gas in the tank.  While changing the plugs, I noticed that a vacuum line was hanging straight down from the carburetor and it was not attached anywhere on the engine.  The line is located next to the clear vinyl carburetor fuel drain line.  I tried to mow again today and the problem still persists.  I have looked online for a diagram showing where this vacuum line should be attached, but I can't kind anything.  Do you have any ideas?  Thanks.

Answer
It may be an atmospheric vent line.  Is the mower still running rough?  Have you removed the engine hood, washed and cleaned the engine area?  This may help identify where the line might connect.

Please send the mower model number so I can look up some information.
Eric