Hi All,
Recently some US builders have asked me about using softer shock mounts than
are supplied with the kit. After changing the shock mounts to the softer
lord, or "O-200 type" on the 914UL factory demonstrator in the US, we
noticed no improvements. Prior the instillation, the engine was properly
balanced. We did, however notice an improvement on another 914UL engine
that had abnormal vibrations after installing the softer mounts.
If the engine is properly balanced in accordance with Rotax service letter
SL-912-010, and running correctly then there should be little vibration with
the factory supplied mounts. However, if the engine is rough, or the prop
is out of balance, than there may be detectable vibration with the factory
supplied mounts.
Softer mounts, however can cause other problems, especially with the 912ULS,
or 912ULSFR as this engine has a higher compression, and can kick back
violently if there is gearbox problem, or if started improperly. The softer
mounts can allow the engine to thrash around when starting, possible
throwing of the air box, carburetors, and various other important parts that
you want secure when you fly.
Hope this helps!
John Hurst
Europa Aircraft
Lakeland, FL
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