rjsdad is correct....by rotating the engine in either direction you have metal on metal with premature wear....this why it is important to properly tune the engine so that it starts quickly...also why it is important to get the engine above 200 deg ASAP..

also one may mention that by pulling the pull start in short qwik strokes and not rubbing the cord against the case will not only start the engine quickly...it helps prevent the coil failing by pulling on the cord to far....and also helps preserve the cord..... they are not lawn mowers

there is 2 methods I use....1 is to put my thumb on the head and the cord between 2 fingers....this allows u to pull in short, qwik and straight pulls...2 I put my chest above the rc engine...so this way I hit my chest before I pull the cord to far...both ways will start the engine right up if properly tuned