[DK914]

A good thing the paddock for the San Diego autocross is on the side of a hill, as I had to bump-start my car ('74 2.0) a couple of times when the starter failed to spin the engine. I can hear the solenoid click, but then nothing. The I'll try it later and it'll work fine, spinning the engine over quickly. The problem doesn't seem to be heat related, and the charging system is in good condition, the battery has plenty of juice and I just cleaned the battery posts for good measure.
Should I replace the starter, or should I try another course of action? I've heard of a Bosch starter relay kit that might help here. Does anyone have any experience with that? Thanks in advance.