fbpx
Jump to Forum..

912 ULS 3000 RPM Vibration

in 912 / 914 Technical Questions 13 years ago
I have a Rotax 912 ULS on a Tecnam Sierra with about 600 hrs. I am getting increasing vibration at 3000 RPM, which happens to be the power setting for a 500 fpm landing decent. The vibration disappears at 3200 RPM and begins at about 2800 RPM. I have synched the carbs, and have recently rebuilt the carbs as part of the 500 hr rubber goods replacement. There was a lot of varnish on the carbs when they were rebuilt, which I removed using carb cleaner. I did not change the jets however, and just soaked them in carb cleaner. The vibration occurs no matter which mag is on. Prop has not changed so at this point I am ruling it out. I don't know if this is a carb issue or perhaps a gearbox issue. Any help would be appreciated.

  • Re: 912 ULS 3000 RPM Vibration

    by » 13 years ago

    Hello Douglas,

    Did you check the condition of the rubber mounts of your engine support?

    Greetz Jan
    Thank you said by: Douglas Gunn
      
    Report

  • Re: 912 ULS 3000 RPM Vibration

    by » 13 years ago

    Jan: Thank you for the reply. I forgot to mention that I changed the rubber engine mounts as part of my 500 hour rubber goods change.

    Doug
      
    Report

  • Re: 912 ULS 3000 RPM Vibration

    by » 13 years ago

    Hello Douglas,

    OK let us continue with hypotheses.


    condition and installation rubber mounting flanges carbs?
    no leakage btw float chamber/carb body: sealing damaged during re-installation?
    filters clean?
    carb vent lines running as before?

    Greetz Jan
      
    Report

  • Re: 912 ULS 3000 RPM Vibration

    by » 13 years ago

    Quote:

    Jan: Thank you for the reply. I forgot to mention that I changed the rubber engine mounts as part of my 500 hour rubber goods change.




    Did you replace and or check to see if the "O" rings are in place under the rubber carb flange?

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: 912 ULS 3000 RPM Vibration

    by » 13 years ago

    Jan and Roger:

    The vibration was present before the 500 hour rubber goods change, but has got more slightly more pronounced since. The "O" Rings were changed as part of the 500 hr rubber goods work, but I have not checked their condition in the last 50 hours. Carb flanges were changed then also, but I don't know their condition at present. Carb vents were replaced and are OK. Don't know about the leakage of the float chamber/carb body and would need to check. Have checked fuel filters from the gascolator to the electric fuel pump and there is no debris. Fuel pressure is normal and there has been no change.

    Would any items listed above cause vibration to occur at 2800 rpm, and disappear at 3200 rpm? If so, how? I don't understand.
      
    Report
You do not have permissions to reply to this topic.
Related Topics
Title Category Replies
Sudden drop in RPM while changing fuel tank 912iS Technical Questions 3
Kitfox 3 with 912 1300 hrs on engine 912 / 914 Technical Questions 5
Rotax 912iS Regulator B w/ Grey Connector Parts 0
912iS Fine filter fittings 912iS Technical Questions 3
Troubleshooting Ignition issues 912UL 912 / 914 Technical Questions 20