Anyone flying a Rotax 912 series engine should pay attention to the "Mandatory SB-912-53" service bulletin. It deals with the replacement of the mechanical engine mounted fuel pump with a newer design. The issue is the use of an electrical fuel pump on the suction line to the engine mechanical fuel pump increases the fuel prsssure supplied to the pump and can cause the mechanical pump to fail, engine stoppage due to flooding, and the potential for massive fuel leakage. Almost all CH 601XL's use a wing mounted electric pump to feed the engine pump fuel. Both my CH601HD and CH750 fuel systems are configured this way. Many builders have installed an electric pump to "fill the carb bowls prior to start" or as a plan "B" in the even of an mechanical pump failure. A couple weeks ago my CH601HD suffered a "sudden engine stoppage" on take-off and I made a very quick landing on what was left of a very short grass field with a fence and large 50 ft trees at the end of the runway. Another 5 seconds of flight and I would be on this site selling parts of the airframe / engine / instruments. I had switched the electric "boost pump" on prior to take-off figuring if the mechanical quit it would be a "non-event"... my mistake. I was aware of an earlier TSB (SB-912-50) on the fuel pump, and assumed this one 2 years later was just a repeat of the first "inspect fuel pump TSB"     (I never read it closely).... again my mistake. A new fuel pump is $175. This is very cheap life and aircraft insurance.  Fly safe..... or at least informed.