BMW R850 Maintenance Manual page 48

Look at the fuel level sender rod while you have the parts out. There should be
an E-ring type circlip holding the float to the rod, but some of the early bikes were
missing these and had their floats bobbing around the tank rather than
registering fuel level.
I carried the assembly back to the gas tank. The O-ring must be pressed down
into the groove, the vent lines forced back on the plate, and install the plate
exactly as removed. Start all six screws, and tighten in a cross pattern. I tilted
the tank back up after this operation to try and get the O-ring to leak. After 30
minutes or so, nothing had come out. I would suggest doing this as well to avoid
having to re-remove the tank to fix a leak.
Reinsert the fuel tank, and the lines pretty much fall into place. I added some
gas to the tank because you don't want to run these roller cell fuel pumps dry for
any reason. I would also coat the fuel injector and fuel pump connector pins with
dielectric grease to deal with the moisture and corrosion that the bike sees daily
in some cases. Reinstall all body work and all the screws you removed.
Tighten the clamps on the fuel lines and reattach the vent lines by the airbox.
Start the bike, check for leaks, and if all is well, ride the hell out of it for another
year!
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