January 29, 1992

SERVICE BULLETIN #11A

SUBJECT:    Rotax 912 CARBURETOR AIR VENT TUBE

TO:    Kitfox™ Owners Equipped with Rotax 912 Engines

FROM:    Denney Aerocraft Company

There have been several incidents reported to Denney Aerocraft, where the above mentioned engines have continually ran excessively “lean” during normal operation, no matter what the needle valve setting. Our investigations revealed that the carburetor Air Vent Lines were lengthened and vented out the bottom of the cowling. The longer tube, especially when vented out into the prop-wash changes the air pressure inside the carburetor causing it to run excessively lean. This can cause the engine to run very lean and possibly seize.

Denney Aerocraft recommends that you leave these vent tubes as they come from the Rotax Factory. We have not experienced any fuel dripping or leaking from these factory supplied vent lines. These Vent Lines are not fuel overflow tubes. If fuel is leaking out through them, then there is a carburetion problem.

NOTE:     IF YOUR FAA INSPECTOR REQUIRES YOU TO VENT THESE LINES TO THE OUTSIDE. PLEASE HAVE THE INSPECTOR CALL DENNEY AEROCRAFT’S TECHNICAL SERVICE DEPARTMENT.