Fuel level sensor - How do they work?

[RiceBurner]

On my Rockster I renewed the fuel filter last week as part of a service and since then, the fuel-reserve light has been playing up.

Initially it was stuck "on" (ie lit). Even a full tank of fuel didn't change that.

But I've now down about 100 miles (commute to the office and back) and during those two rides, (I topped up that morning), the reserve light has gone off, then back on again at random intervals (about 10 times per trip).

Initally I thought it might be something to do with leaning the bike and changing something in the tank... but I couldn't replicate that.


So - the main question is... How is the fuel level actually sensed? How does the sensor work? I"m pretty sure it's not a lever with a floating ball on the end, so how is the level actually ascertained?

The Rockster just has a reserve light, like the R1100S (same instrument panel), so I'm assuming the fuel-level sensor is the same too.

[nab 301]

A bit of a late reply , I had a photo but I can't locate it , and I've replaced the filter a few time in my 20 yrs of ownership but for some reason I can't remember what it looks like Part number is 16142306895 for the 11 S and I think it's a white plastic cylinder with a float/ slider inside all mounted on the back plate beside the pump and filter . That number doesn't seem to come up for the Rockster . Some R models have a float on a piece of wire but afaik not the S
http://mcsoperformance.com/pompe-essence-jauge-filtre-/3087-jauge-a-essence-kit-complet-r1100s-bmw.html