Belleville Washers in Gearbox of Rotax 912/914 Engine
Rotax 912 Gearbox. Note: There is no fuel pump since we have an all-electric fuel delivery system . The Belleville washers in the Rotax gearbox, which exert pressure on the so-called dogs, must be replaced when they become worn beyond the required spec. This should not happen if the Belleville washers are replaced according to the schedule specified by Rotax. For our 912UL engine, this is to be done after 1,000 hrs. Now we do all repairs and overhauls on condition and not on a fixed hours-in-service schedule. If you also follow that rule, proved by the US Air Force in WWII to drastically reduce failures, then you want to look out for the symptoms described below. First indication of worn Belleville washers is the following: You are past 1,000 hrs, and engine idle is a bit rough. Not too bad, but no matter what you do, such as balancing of carburetors , the roughness does not go away. Suppose you ignore this seemingly minor symptom. The second indication of worn Be