Got a problem here that is driving me nuts. I have a Briggs engine, model 190402, type 2643. Start's on the first pull and runs perfect. For about 5 minutes. Then dies. Restarts on first pull sometimes, but then dies again in a couple of minutes. Or sometimes wont restart for 10-20 minutes or so. I have replaced the coil, new plug, rebuilt the carb, replaced the fuel line and filter, and cleaned out the gas tank and refilled with new fuel, even changed the oil. Most of this was in desperation, as I ran out of idea's. This is on a rear tine tiller, and it just runs perfectly, but won't keep running more than a few minutes at a time, and after you restart it it a few times it won't start at all for 20 minutes or so. Any ideas? Am losing my mind here.