I have recently purchased a Stihl BR 400 backpack blower and I have had nothing but trouble out of it. It will sometimes start, and I say sometimes because sometimes it will spit and sputter, then cut off and not start due to flooding. That is my first problem, my second problem happens after I get it started. It runs good for about five or ten minutes then it will start spitting and sputtering and all of a sudden cut off and it wont start back again. I have emptied all of the gas out of the tank and replaced it with new mix, I have changed spark plugs, but it is still messing up. Any advice would be greatly appreciated.