LSA pilot experiences a rough running engine fifteen minutes after takeoff from an airport where an oil change and routine maintenance were preformed. A precautionary landing is made on a service road and the Mechanic is called. A loose carburetor vent hose is discovered and corrected and the reporter continues his flight.

Narrative

I took off after a routine oil change and maintenance on my aircraft. 15 minutes into the flight my engine began vibrating and running rough. A strong smell of fuel was also experienced. Not knowing what the problem was I advised Center that I would be doing a precautionary off airport landing. Center advised that the closest airport was 12 miles east. Since I did not know why the airplane was vibrating and was losing RPM I decided to land on a service road which was directly under me on my route instead of trying to reach the airport. I landed the airplane with no problem on the service road. No injuries or damage to the airplane was done. I advised an airplane overflying to relay to Center that I had landed okay. I contacted my Mechanic and requested he drive down to examine the engine. After a few hours my Mechanic arrived and inspected the engine. He found a lose carburetor air vent hose which had come off. This flooded the carburetor and created the low rpm and excessive vibration. The Mechanic reinstalled the hose; rechecked the carburetor and engine and determined the problem had been resolved and the airplane was airworthy. I took off from the service road without any issues and landed at my home base airport without any further issues.