From years of running dirt bikes i had grown accustomed to a dirty air filter causing a 250cc dirt bike t foul a plug before it would puul dirt through the filter. I had an incredibly strong running v-spec that almost never needed tuning and ran it too long with a dirty filter and it pulled dirt all the way thru the filter and would still run decent ,so I had no idea it was sucking dirt all thee way thru. RUINED...... Any time you find yourself turning the screws and not getting the desired result take it as a WARNING that something else is going on and you are being offered the chance to toast your engine.These engines will do some weird stuff, I am still learning everyday!!!I have a couple of really BIG saws that have to idle for 3-4 min. to allow for the expansion differences in the metals.