I went to go fire up the air compressor and it just hummed, and shot sparks out of the switch box. I had to pull the motor off and it was packed with mud dauber nests! I hate those things! Got it cleaned out and re installed.
But this is another reason to plug your exhaust when you are not flying!
The can cause airplanes to crash too.
http://en.wikipedia.org/wiki/Mud_dauber