High pressure spray will force water into electrical connectors which can cause corrosion later. The connectors can resist normal rain and road spray.

High pressure can also blow gaskets out from between the metal surfaces, blast grease out of "permanently lubricated" bearings, and in general force water into places it shouldn't be.

You might be further ahead to spray Simple Green or another de-greaser on the oily surfaces, let it soak, and rinse with a gentle spray from a garden hose.

It got dirty a bit at a time, so don't be in a hurry to clean it! Several gentle applications are usually better than one big blast.

BCingU, Jim.