on this B&S 16 HP self propelled blower i use, after about 70 mins of run time the muffler gets red hot and begins to glow, what's up with that? the oil has been changed, and is at the right level, is it just not made for continuous use? I don't really want the thing to blow up, if i remember correctly, it is an At water product, called air-broom. any ideas? thanks guys.