I have four dirt bikes that I hose down when the grime becomes unbearable. Although I'm not totally anal, I am careful about not sticking the hose down the exhaust or squirting water directly on the sensitive parts. Call me too cheap to buy the trick exhaust plugs or whatever, but I keep a few slightly used surgical gloves around and, instead of throwing them away, I stretch them over the tailpipe to keep water out, finally tossing them when I'm done.
Got a Trail Tip? Send it and some pictures to karel.kramer@sorc.com, subject: Trail Tips.