The ribbing on a Harley engine is designed to dissipate engine heat.
Removing oil stains from a Harley Davidson engine is a tedious task unless the engine has been removed from the bike and hasn’t been chromed or painted. Oil stains on the engine form when an oil gasket leaks oil. Dust collects on the oil stains and acts as an insulator which can cause the engine to run at hotter operating temperatures than normal. Replacing worn gaskets should be done before cleaning the stains to avoid recurrence.
1. Cool the engine completely by turning it off and letting the motorcycle sit for a day.
2. Lay a piece of painter’s plastic on the ground.
3. Roll the motorcycle onto the plastic and put down the kickstand.
4. Mask the exhaust system and the engine frame with blue masking tape. Cover the backside of the front tire with a piece of masking paper. Tape it in place by wrapping pieces of tape around the tire. Put tape along the backside of the front tire forks. Mask the bottom sides of the gas tank. Mask all other parts that will not be cleaned to avoid splatters of mineral spirits on them.
5. Set the toothbrush in the half-quart container with the bristles in the bottom.
6. Pour mineral spirits into the container until the bristles of the toothbrush are covered with liquid.
7. Grab the toothbrush and scrub its bristles on the oil stains in a back-and-forth and side-to-side motion. Use circular scrubbing strokes on large flat areas of the engine and small back and forth strokes in hard to reach places. Dip the toothbrush repeatedly in the mineral spirits after each scrubbing, to remove oil from the bristles.
8. Rag off soiled liquid on the engine after each scrubbing is completed. Continue the scrubbing and ragging technique until the oil stains are removed.