Rubber Sleeves in K Bike Fuel Tank

[Motiv8ed]

Rubber Sleeves in K Bike Fuel Tank?
What’s the purpose of these rubber sleeves on either side of the fuel pump mounting bracket and can they be removed without operational consequence? Mine are starting to come apart and I’m in the middle of replacing pump, fuel level sender, cleaning tank etc, so I want to be able to close things up and sleep at night afterword   

[jagarra]

If they are anything like the rubber mounting on my R1100, it is to keep the vibration from the pump operating to pass to the tank.  Sort of isolating the pump.

[Laitch]

If they are anything like the rubber mounting on my R1100, it is to keep the vibration from the pump operating to pass to the tank.  Sort of isolating the pump.

+1 Many owners have found them lying on the floor of the tank when they've opened the tank to replace fuel filters or hoses, or not found them at all. 

[Motiv8ed]

I wonder if most just leave them off or replace them….and if replaced, what do they use? Can’t seem to find them anywhere.

[Scott_]

You could use some 'in tank submersible grade' fuel hose and slit it.... would serve the same function.

[Laitch]

I wonder if most just leave them off or replace them….and if replaced, what do they use? Can’t seem to find them anywhere.

Like Scott_ indicated, they're made of the same type of submersible fuel hose that's connected to your moto's fuel pump; slit pieces and install them. My moto's tank didn't have them so I haven't replaced them but now I'm getting a strange attraction to them. 

[Motiv8ed]

Funny! Through your humor I surmise you’ve not discovered any negative consequences associated with the absence of these in your tank….noises, vibrations, fuel starvation etc.

[The Mighty Gryphon]

I've had five bricks, and so far i can't recall any of them having those rubber bits in the tank.  I suspect they were added by a previous owner because of a noisy fuel pump.  Those rubber bits don't look to me like anything the BMW over-engineering dept would design for a factory bike.  If they were indeed a part of the tank wouldn't they be shown in at least one of the parts diagrams?

If they haven't dissolved into a gooey mess you can leave them alone or if it makes you feel better you can get a couple inches of submersible fuel line and make a couple new ones. 

I guess that I'm fortunate that none of the bikes I've had made any fuel pump noise until they were in the last 25 miles of the range available before the tank was totally empty.  I always regarded that whining noise as a final non-negotiable warning that I was not far from being stuck on the side of the road if I didn't attend to the fuel situation.

[Laitch]

I surmise you’ve not discovered any negative consequences associated with the absence of these in your tank….noises, vibrations, fuel starvation etc.

None have occurred in 60,000 miles but I may not be as sensitive to such things as others are, except maybe fuel starvation but those dampers wouldn't have much to do with that unless they prevent vibrations of the pump mount from knocking a hole into the tank wall and all the fuel spilling onto the engine and into my lap as a consequence; although if that were to happen, firefighting would like be the first event rather than fuel starvation.

[daveson]

Some of my bricks have them,  it's a safe bet they're for vibration. Maybe this is why some people say the pump gets noisy when the fuel level gets low, you could remove them as a test. It's good to know they can last for years without them.

They slowly vibrate upwards because the top is open and they aren't retained. Once they have fallen out it's difficult to see where they came from, so I guess a lot of people throw them away. They don't look like they belong anywhere cause they're not hollow but solid with a slot in them.

[Laitch]

. . .  it's a safe bet they're for vibration. Maybe this is why some people say the pump gets noisy when the fuel level gets low, you could remove them as a test.

In many cases, the pumps make noise when fuel is at an excessively low level in the tanks because fuel on the pump side of the tank is at a lower level than the other side. BMW created a workaround consisting of a hose attached to the fuel return pipe then routed to dump fuel on the the pump side of the tank.

[daveson]

True, and I wonder if removing the dampers makes it louder, especially if the pump support plate is above the fuel level.

My brick has the dampers and it hasn't been an issue with me, but I use a helmet and ear plugs, and I don't let the level get under quarter full, except once.

When I got my brick the fuel level gauge didn't work so I just used to lift the filler cap and make a guess. After one bad judgment call, it started sputtering a few miles before the nearest country town, I leaned the bike to the left while riding, it picked up, and I just made it. I don't remember it being noisy but my mind was probably preoccupied with the dreaded thought of pushing it or abandoning it and walking.

[daveson]

Actually, maybe it's to allow the tank to expand and contract, or to move, without putting a buckle in the sidewall of the tank, and the rubber around the pump is the one that isolates the pump from the tank.

[daveson]

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