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.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.