I purchased an MVVS 2 cc diesel with the R/C carb for 8 years or so. I traded for an airplane about two years ago. A good engine and I should have held on to it. I never had that problem with it. When I did have that problem back in the 1950's and 1960's on 2.5 cc diesels it was solved by balancing the prop and if that did not work go to a different diameter and/or pitch prop to get in a different rpm range. If it is vibration related this may work.