Rough running 914

[rhtrudder]

At around 4500 revs my engine definitely has increased vibration ,below 4000 and above 5000 it’s good , I think I come across this in another thread, it’s fitted with a O2 sensor so I know the mixture is correct, prop been balanced,  could this be harmonics , has anyone else come across this 

[skippydiesel]

This may help - From Rotax Owners Forum;

https://www.rotax-owner.com/en/912-914-technical-questions/10049-rough-running-around-5000-rpm

 

In the above case it seems likely the cause is  a warn dog clutch