What's the problem with my DW362, type 4 circ saw?

While cutting concrete with a masonry blade, I heated the saw up to a point where it started to spark at the motor and then stopped running. After letting it cool down for a few hours I tried the machine again. It "works". However, although the circular saw runs, it continues to spark profusely at the rear of the motor.Before I change a bunch of parts I was hoping someone could pinpoint the problem for me. Thanks, Eric