RPM Drop in 912ULS

Assuming adequate fuel return lines fitted, vapour lock would be removed/corrected by switching on the Boost pump😈

Thank you, Harold!  I have been using Mogas (98 Octane from Texaco); it´s the fuel I have used for 700 hours with no problem.  Although 100LL is available at my home airport, I stay away from it because of the lead buildup in the engine, which increases maintenance requirements.  Vapor lock my indeed produce the symptom I have, but is very unlikely given the temperatures we operate.   Most of the operations of this Aircam and many other Rotax are near this Airport.  I will report back when I find something else.  Thanks again!

Thanks @Jeff, two events occurred at high altitude and the first one at 5000".  I have always been using Mogas as per Rotax recommendation.  Thanks again!

Francisco,

I don’t know much about Mogas in Columbia, but here in the USA this is the time of year when automotive fuel in most states changes from summer gas to winter gas. Summer gas has a vapor pressure of about 7 PSI (similar to Avgas) and winter gas can be as high as 13.  So this is the time (here) to be careful because temperatures can still be warm and make using Winter fuel more risky.  I’m with Harold on this, run one full tank of Avgas and see if the problem is resolved. 

Francisco is driving 912ULS (carburettors). Unless there is something very peculiar in his fuel reticulation system (design), in-flight fuel vaporisation, is  unlikly.😈