Using a pressure washer to wash your motorcycle is an extremely risky game to play. If there is serious grime all over your bike, using a pressure washer could be a good idea due to easier displacement of muck. With this being said, never ever consider using a pressure washer on brakes, as this could cause water to slip past the piston seals and cause the leaking of fluid or even worse, water getting into the mechanisms of your bike. This will cause the weakening of the breaks over time, diminishing their overall stopping power. The same can be said for the wheel bearings: if the pressure washer gets into them, it will clean off the lubricant and dry them out, therefore formulating a pretty costly repair bill.