The issue that this lawn mower has is when it gets warmed up the engine pull start acting up going like a high pitch to a low pitch, then it will just stop. It will start back up and die again doing the same thing. I have already changed air filer, carburetor now, replaced oil etc. and it still does it. Any suggestions? I even removed the cap on the gas tank and it will still do it. I read that now here and tried it too. Thanks