Boxerworks.com

I've had a 43K mile 1993 R100R less than a month and am slowly going through it, doing all the major service "by the book". One job involved replacing the petcock screen filters. I removed the tank so I could remove the petcocks without spilling gas everywhere, and found two metal tubes sticking out of the tank. One of them leads up to the trough around the fuel filler (#1 in the photo) but the other seems to lead into the tank itself (#2). Shaking the tank a bit resulted in fuel spilling out of that small tube. That can't be A Good Thing. (The tubes are plugged in that photo, but they weren't that way on the bike.) Frightening to think I could have had fuel leaking out when cornering or stopping hard.

Another photo is of the airbox. There is a 1/4" plastic fitting that goes nowhere. (Circled.) Not easy to see is another 1/8" T-shaped fitting, also with nothing attached.

Reading through the official BMW repair manual, it appears that there should be all sorts of solenoid valves and tubes running hither and yon. That might also explain the brackets under the tank that have nothing attached. I'm assuming one of the P.O.s removed all the emissions stuff.

The bike runs fine, although the plugs are darker than they should be. Maybe the missing emissions makes it run richer. I'm think of capping off the smaller tube and running a drain hose out of the larger tube into the airbox.

Thoughts?

If I am recollecting correctly (say that 3 times fast),
all that SHED crap was BMW's last ditch effort at making an antiquated fuel delivery system meet certain emission criteria.
No raw fuel vapours were supposed to reach the atmosphere. No more vented gas caps, leaking carburetos, etc...

I won't get into the socio-political aspects of removing anti-pollution systems from vehicles, but BMW never had that system in Canada and Europe, and as far as I know, we're still breathing.

The only important thing to remember is that your tank must be vented. Air has to be let in as the fuel level decreases. I think that's what the number 2 hose is for when you do not have a vented gas cap. The number 1 hose is for any gas overflow while filling and/or rain water around the gas cap to drain. They should be routed to come out anywhere under the bike, away from the exhaust system.
That other parts can be left in place or removed, makes no difference to how the bike runs.

Snowbum has an article that deals with this system and how to "update it" shall we say!!

Kurt in S.A.

Thanks for the confirmation. There appears to be a bracket for the the overflow pipe. I will route the vent to the airbox.

Don’t know how to delete this duplicate post

Not sure what you meant by "There appears to be a bracket for the the overflow pipe."
There is a brace that goes under the tank from side to side, I assume to reduce flexing of the tank.
It attaches to the threaded bracket next to the pipes and across to another threaded bracket on the other side of the tank.
I don't believe there is any bracket as part of the overflow line.
see part #11