Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL) or certified (A and F) engine and there are four main models (injected too) to date. The original engine is the 80 hp 912, from which the 100 hp 912S was developed and Rotax also has a 115 hp turbocharged 914 engine. In 2015 Rotax announced the 135 hp fuel injected turbocharged 915iS.
Recognizing the different models is easy: the 912 has black cylinder covers, the 912S green/blue (blue for the french market) and the 914 has red covers and a turbo. These are the most obvious differences.
SI-912-020-914-018, Purging of the lubrication system
Excerpt from the document:
ROTAX was informed of a limited number of engine failures in the field resulting from a lack of proper oil purging after the engine had been first installed and/or the engine had been re-worked. This Service Instruction should help to make sure that the engines do not suffer such failure in the field. As air can be trapped in the valve tappets and cause valve train failure it is very important to complete these instructions in their entirety.
To continue reading see the pdf below: