Hawk crankcase breather....
 

Watch the hose from the engine to the airbox. My hawk is a little over a year old and has never sat outdoors. Less than 600 miles on it and this is the breather hose as of today.....

Looks like a chemical reaction ate it away . That's the way my banjo nut for front brake looks by reservoir . BTW I was riding my new to me WR250R up by you Sunday . :tup:

Unfortunately the Hawk's front brake boot,the hydraulic piston cap,the battery bungee cord and the crankcase hose are of poor quality.

Gotta love that Chinese rubber. It's really the only bad part of these things left to deal with anymore.
Also, the stock fuel line loves to break down internally and toss micro-chunks of rubber at your jetting too. Looks great from the outside!