Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL), sport (S) or certified (A and F) engine and there are four main models (fuel injected too: i models) 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 BRP-Rotax announced the fuel injected 141 hp turbocharged 915iS.
Rotax BRP has developed new floats for the carburetted engine they sell. Due to a deviation in the manufacturing process of the floats a partial separation of the outer skin because of resonance vibrations during engine operation may occur. These separated particles might lead to a restriction of the jets in the carburetor. As a consequence the fuel supply to the affected cylinder bank may be reduced or blocked. Possible effects are a rough engine running behavior with reduced fuel flow, up to a major power loss or engine shut down with blocked fuel flow on the affected carburetor.
And: due to a deviation in the manufacturing process some floats could absorb more fuel thus having more weight. This leads to a loss of float buoyancy and wrong regulation of the fuel in the float chamber. Possible effects may be a rough engine running, especially at low speeds and under circumstances loss of performance and/or fuel leakage in the area of the carburetor.
SI-912-914-029, Introduction of new floats.
Excerpt from the document:
In the course of continuous development and standardization, new floats (pair) ROTAX® part number 861188 have been introduced. These new floats (pair) are manufactured with a higher compaction rate and contain a recessed brass guide.
In addition to this Service Instruction the following Alert Service Bulletin, Service Bulletins and Service Instructions must be observed and complied with.
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