R1100s low fuel sensor repair

[850dunstall]

So this is an update on the repair of an R1100s low fuel light failure.

history, low fuel indicator did not come on and i ran out of fuel, found another post on the Pelican forum of similar situation., if its broken I can fix it. The r1110s only has a low fuel sensor, but no display. So it is different from all the other oilhead bikes, ( except possibly early r1100rs).



the sensor is a round white canister located inside the fuel tank attached to the fuel pump plate. It is a simple Reed switch surrounded by a cylindrical floating magnet. as the fuel level changes the magnet causes the the tiny filaments in the switch to make or break contact, which sends a ground signal to the fuel level dampening unit which then turns on the low fuel light. a bit complicated and not direct.

when i open my white canister i discovered a broken reed switch. I ordered a pack of replacements from amazon 2mmdia x 14mm long (very important you need to get the N/C normally closed option), these things are tiny, i disassembled the pieces and reassembled with the new reed switch. positioning of the switch is somewhat critical, otherwise the sensor could cause an early or late signal. anyway it seems to be working. i need to run a tank and see if its really fixed. there is also the possibility that the dampening unit has gone flacky, at which point it can indicate good fuel level even when the tank is empty, or empty even when the tank is full.

if you use the N/O (normally open) reed switch the light will be on until the fuel level drops below 4litres.

[mgp steve]

Thanks for the tutorial!

[tomvv11]

Thanks indeed. I've repaired the other end of these wires before but this is next level reverse engineering. I'd thought it was a simpler mechanical switch on the float.
Does the slotted brass ring sit on top of the inner small diameter white tube that the magnet slides along?
My reserve light comes on very consistently after 3.5 gallons has been consumed. The tripmeter/3.5 tells me fuel mileage and I can then determine exactly how much range remains.
Having blown it once uphill from a gas station I know my tank's capacity is 4.931 gallons, but I call it 4.8 to take pump inaccuracy into account.

[850dunstall]

Originally Posted by tomvv11

Does the slotted brass ring sit on top of the inner small diameter white tube that the magnet slides along?
...

the little brass ring is pushed onto the end of the white tube. the tube has 2 tits that hold it in place, so the resoldering needs to be neat.

I should add the the last of my posted pics actuall was borrowed from someone else post here yrs ago with the same problem,