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rotax 4-stroke - cylinders / valve / heads
912UL, 912A, 912F, 912ULS, 912S, 914UL and 914F Engines
All information provided here is correct at the time of publishing to the best of our knowledge, but Rotax recommendations may change at any time without our knowledge. It is the engine owners responsibility to ensure that the engine is fit for flight at all times. The information is provided here free of charge and with no obligation from us to the consumer. To ensure that you have the correct and most up to date information, you should refer to the current Installation, Operators and Maintenance manuals for your engine. The information provided here may not be valid for aircraft outside the UK. Click here for ConAir SportsTerms& Conditions, including website usage policy.
4 cylinder 8 valve centrally mounted camshaft with pushrod overhead valves.
Cylinders are Nikasil lined aluminium bores proven to be exceptionally hard wearing and reliable (and do not suffer from corrosion in the short term).
The 912 & 914 series engine range have an extremely robust top end with air cooled cylinder and liquid cooled heads. The engines have been found to be extremely reliable even in the most demanding applications.
Tests should be carried out using a differential compression tester. Compressions test to be carried out at 80-87 psi and even on high hours engines losses of only a few percent are common. A normal automotive style compression tester can be used for fault finding.
There is no head gasket to blow. The cylinder and head are lapped together. Any leak between the head and cylinder might require the mating joint to be re-worked. A blowing joint is sometimes an indication that the engine has been overheated. The coolant only circulates through the head so no chance of a blown gasket allowing coolant into the oil.
Coolant leaks are uncommon but can be a sign of overheating. The coolant elbows are threaded into an adaptor plate or directly into the head and the thread is sealed with Loctite. Moving the elbows or overheating can damage the seal which can be repaired by removing the elbow and applying fresh Loctite.
If the coolant is lost for any reason the engine can run for a limited time however the operating limits are likely to be exceeded and the risk of an engine failure or permanent damage is high.