Chainsaw Repair

Let me lay on another factor .At 12000 Rpm the engine would be firing 200 a second .The human ear cannot accurately determine with that frequency of change if the saw is firing every other stroke or every 4 or 6 strokes .It can determine something is different though .
 A little background on myself at this time .In my tour of duty in the US Navy in the submarine service I was a sonar tech.At that time we could by nature of sound determine  propeller turns per minute,type of propeller ,type of propulsion system etc all my ear ..However things like diesel engine RPMs ,number of cylinders and numbers of engines,supercharger speeds,steam turbine speeds  we had to rely on instrumentation to slow the revolving noises and band pass filters to block  certain ambient noises to accurately determine high speed sounds

Again more trivia but the bottom line is perception being "4 cycling " would be accurate in the discussion based on what the ear hears .