What is this line?

[Chris Costello]

Alright, so I have a 1981 Yamaha xs650 which has been sitting for the past ten years. Over the past few months I've been dissembling and cleaning the bike. However when I went to put everything back together I found a line that starts near the battery box and goes down the bike. Included are some pictures of the line. I don't remember disconnecting it from anything, although I'm that I disconnected the line and just forgot about it. Thanks for the help.

 

[650Skull]

Acid Battery vent hose. VIP

 

[CoconutPete]

Hose is probably pretty crusty at this point and probably slipped off without you even noticing it when you pulled the battery. Assuming of course, there was a battery in there when you started.

 

[Paul Sutton]

The positioning seems good i.e. well away from the chain and low to the ground. When they get old they do just drop off when you take the battery. If they are not re-connected then the acid vapour and drops vented from the battery cause a lot of rust problems in the battery housing area.