I am 75, try to maintain my own equipment, but this one has me stumped. This saw will start readily, runs good for about 5 minutes, then starts to bog. I suspected a fuel delivery problem and changed the pick up filter, air filter, and cleaned the spark arrestor with no improvement. The part that has me stumped is that it will start and run fine again after leaving it sit for 15 minutes but then does the same thing. It seems like if it was running rich and fouling the plug that it would not start back up and run the second and third time. BTW, full tank of fresh gas. Does anyone have advice as to what to try next? Thanks!