I do one thing religiouly with magnum 4 strokes every time I fly and it works great . A buddy told me a long time ago that the original designer for OS went to design magnum years ago .While they are great engines , they are not as smooth internaly from the manufacturting process .
ANy way , he said before every start remove the glow plug and put a drop of after run oil in , I swear it works like majic , these engines love oil !!!