Jemima has a 912S. It is mounted on a bracket on the root tube by 4 bolts into the bottom (only) of the block. The engine wobbles around a good bit on start up and shut down but actually runs quite smoothly the rest of the time although it does not much like full idle during descent.
A number of the non certified 912S engines were supplied without the clutch for a while. The clutch needs regular adjustment and they hoped to do away with that. The reason given for the clutch was to safeguard the crank in the event of a prop strike. Unfortunately a considerable number of engines without the clutch have developed gearbox vibration at about 3k+ revs after about 70 hours and mostly the owners have been obliged to go with Rotax suggested upgrade of installing the clutch. (Ouch $$$$)
When I first set up the engine I used the factory recommended idle at about 1400 revs but as the weather got colder it occasionally got lumpy. Our group (about twenty of us) were discussing it at the time and we reckoned we might go for 1600 to a max of about 1800 for the Winter. Finally I've set mine for 1600 year round.
Last November I had the engine quit on landing when I pulled it to idle. Twenty seconds later she restarted and idled just fine. I did all the checks and then flew another circuit (close in!) and the same thing happened. According to Rotax the 912S is not subject to icing but I have seen a couple of pictures of a thin film of ice formed on the inside wall of the carb, I reckon it is just enough to close off the air when the butterfly closes but does not affect airflow when the throttle is open. As soon as she quits the throttle body warms up and so she runs.
As it happens it was only a few days before her annual and she now has new plugs, also I have only flown since in weather dry enough to turn running bull into jerky in about twenty minutes. so no re-occurrencies. We'll see. . . . .