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.
During a manufacturing process check a deviation was found in certain crankshafts in Rotax 912 and 914 engines after a certain serial number. Only newer and rebuild engines seem to be affected by this issue.
This check / repair involves removing the gearbox and performing a non destructive penetration check to detect cracks in the thread runout area.
SB-912-059-914-042, Crankshaft manufacturing deviation.
Excerpt from the document:
Due to a deviation in the manufacturing process some crankshafts may have a crack formation occur on the power take off side. These cracks can cause a breakage of the crankshaft support bearing and may lead to engine stoppage.
Checking of the crankshaft journal (power take off side) for ROTAX® engine type 912 and 914 (Series). Required before next flight, but at the latest before 01. April 2012. The checking of crankshaft journal (power take off side) identified by the engine serial number (S/N) listed in section 1.1) must be conducted according to the following instructions in section 3.
To continue reading see the pdf below: