what is this line? purpose?

[stephen2us]

Looking over my xs400, i found this line with two clips on it... it's slightly leaking what I believe is fuel at the top portion, i assume the crimp isn't a big deal either? What is this line, purpose, and is a slight leak from the top a big deal? hopefully, the pic shows up, I'm new..the pic isn't right side up...
Thanks
Steve

 

[Norman1950]

It is a crankcase vent.

 

[xschris]

Make sure it don't leak and it is not crimped. Otherwise dirty air can get into the motor and the motor will not vent like it should.