On my 2006 Heritage Softail Classic, there is a black canister, slightly larger than a beer can, on its side, located slightly beneath the oil can and behind it, about eight inches down. From the right side of the bike, you can see that this end has a nippled knurled end, which appears to indicate that it takes a medium size hose, but which is missing. It looks like some kind of air canister. If it is missing the hose, I want to replace it. Can someone decipher what its for? I can provide pictures if needed. Thx

 

If it is a California bike it may be part of the pollution stuff. Go to Ronnies HD website where you can look at the parts fiche for your model. They will show you drawings and part numbers. To find the HD # put items in the basket and go through the order placing routine, when you will see it displayed. You don't have to order through them if you don't wish to. That should answer your question.

 

It's a carbon filled "filter" for air quality purposes. Canister connects to the neck of the gas tank to accept vapors from the tank. I believe it also feeds it's vapors to the carb to be burned off.

When modifying a bike, like replacing a carb or beefing up the ride for performance these are often simply bypassed, and plugged off.