That's the crankcase breather hose. It collects all the noxiousness produced when engine oil heats up when the bikes running, then condenses when the engine's shutoff.
It's routed thru the airbox rather than to the atmosphere as a kind of minor static emission control thing. It's plugged to keep road dirt from entering the airbox, and at the same time contain the stuff until it can be drained at the next service interval and be disposed of properly (like waste oil, which it basically is). And yes, you need the plug (unless you want really nasty brownish liquid on your pipes, wheels, tires, driveway etc.) -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
