I have a Airmaster CS prop on my Kitfox that has been leaking grease since new. I now have over 100 hours and still leaking grease. I was never able to get answers from anyone. I finally found buried on the Airmaster website they have just recently issued Service Bulletin APL-SB18 and have acknowledged this is an issue. If you are having the same issue you can get a larger O-ring from Airmaster to fix the problem according to the SB.