Another Fuel Tank Question

[Dave 2]

Once again I am suffering the consequences of NOT taking a photo of the underside of my gas tank. With the tank turned over I have a (outlet?) pipe which extends about 3/4 of an inch It looks to me to be for a fuel line.  I can't figure out what it's function is or what parts are required to finish it off.  On the opposite side is a small threaded piece with a nut welded to it. Something obviously used to screw into it. Any ideas what that is about? Thanks, D2

[Bob_Roller]

It's an overflow drain for the fuel filler, there should be a small hole next to the fuel opening .

If you happen to overfill the tank, or get surge in pressure and get spillage .

It drains onto  a hot engine ( nice feature ) !!!!!!!!!

I put a piece of fuel line on the tube and get it routed  so any fuel goes onto the ground, instead of on a hot engine .

[montmil]

When I first purchased the '81 R65, I noticed the "drain hole" looking thing in the fuel tank's flange. Not sure what it was so poked a long pipe cleaner down into it. Surprise! It came out on top of the engine. Fuel slop over flow.

I didn't care for a tube running straight down beside the engine so added a 90-degree nylon fitting. Routed the tube back and down to where I found an existing hole near the passenger foot peg/swing arm junction.

Let the tube extend enough to clear the chassis.

I also found this safety feature missing when I acquired the '83 R65.

[georgesgiralt]

Hello !
Having bought my bike new, I know... The bit of metal tubing is, as other say, for the overfill.
Put a fuel line in it, route it along the chassis and make it line with the battery overflow tube. They are normally going out at the same spot.
I was told the threaded nut under the tank was for a holding device during painting at the factory.

[Barry]

/0#0

I was told the threaded nut under the tank was for a holding device during painting at the factory.  

That was my thoughts when we discusssed it in an earlier thread.

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1256925569

[bruce_launceston]

As Mont said the factory fitted overflow tube runs across to the right hand side, down the frame tube and slots into a small cutout in the pressed metal footpeg / muffler mount just near the rear brake light switch.
Fuel hose outside diameter is too big, just use a piece of ligher weight rubber hose, perhaps window washer hose?

Any overflow eg: overfull tank parked in the sun will see the fuel overflow not onto a hot motor but onto a hot exhaust, oh well that's what BMW designed.

[Dave 2]

Thank You all for your responses, and the link to the threaded gismo under the tank. I like Monte's elbow idea to get the fuel line headed toward the back of the tank and then down to the battery overflow hole in the frame. I'll have some new photo's posted soon. [smiley=bmw_smiley.gif] D2

[Barry]

I don't think there is any doubt that the overflow should be routed as suggested to exit with the battery vent tube and that's how mine was when I got it, including possibly the original black rubber tubing. What the original design lacks  is the 90 deg bend that Monte suggests. Without that, the bending radius is such that the tube is visible below the bottom edge of the tank which isn't a tidy solution.  They should have bent the outlet towards the rear so that the rubber tube was well hidden behind the tank. In the absence of that I'm on the look out for a 90 deg bend.

[montmil]

... In the absence of that I'm on the look out for a 90 deg bend.

Hardware store item. I did shorten the leg that ties into the overfill drain.