Author Topic: Removing the gas tank  (Read 16585 times)

Offline frankenduck

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Removing the gas tank
« on: May 31, 2011, 12:52:43 PM »
CAUTION:   The fuel system on K bikes is pressurized by the fuel pump.  If your bike has been run recently then there will be pressure built up in the fuel lines.  If you're going to be to disconnecting any fuel lines then it's advisable to wear some safety glasses and not to use a Bic lighter or a Tiki torch as a worklight.  When you disconnect a pressurized line then chances are that some gas will be sprayed around.  You might want to have some rags around to clean up any spilled gas.

0) If you can, run the tank fairly low before removing it. That will make it lighter and easier to work with.  Also, you're better off putting the bike on the center stand before doing any of this.

1) Remove the seat and side(battery) covers.

2) Follow the clump of four wires coming from underneath the rear of the fuel tank and find it's connector under where the right battery cover was before you removed it.  Disconnect that and get the clump of wires free so that you will be able to pull the tank back.

3a) 85 and earlier K100s: Remove the 10mm hex bolt that holds down the bracket on the rear of the tank.

3b) All other K bikes: There are two posts at the rear of the tank that go through some black rubber grommets in the frame.  Under each grommet is a large (usually shiny) C-clip with a lip on it that fastens around each of two posts at the rear corners of the tank.  Grab the lip of each C-clip from the side with some needlenose pliers and pull the C-clip straight back twoards the rear of the bike.

4) Lift the rear of the tank and pull the tank backwards.  Sometimes, if it hasn't been removed in a while, the posts will stick in the grommets.  I usually use a short section of 1x2 or 1x4 lumber to pry the rear of the tank up.

5a) 2 valve K bikes: There isn't a lot of slack in the fuel lines so you won't be able to pull the tank back very far without disconnecting the fuel lines.  If you're just going to be working in the relay box then you can often get away with just propping up the rear of the tank with a block of wood.  For anything more serious you're going to have to remove the fuel lines from the front left corner of the tank.

5b) 4 valve K bikes: There's a fair amount of slack in the fuel lines.  Many times you can get away with just pulling the tank back or putting a tall chair next to the bike and supporting the tank that way without having to remove the fuel lines. (Put some towels/rags over the painted bodywork to avoid paint damage if you're going to use this approach.)

Side note: Under the right rear of the tank are two pipes pointing straight down.  The front one was part of CA emissions crap and may or may not be connected to a pipe on the top front of the engine block.  It doesn't matter.  The rear one is for fuel overflow and comes from the hole on the left side under the gas cap.  Some bikes have a hose connected to that that runs down the right side of the bike and drains to the ground inside of the right pegplate.

Other bikes have what commonly referred to as "the cup" mounted to the frame underneath those two pipes.  The cup should be connected to a hose that runs down the right side of the bike and drains to the ground inside of the right pegplate.


The BMW part name for the cup (red item above) is "air accumulator" and it's part number is 16132307467.  The drain hose (green item above) is part 16131455350.

Gas draining into the cup is why you might get a faint whiff of gas after filling up on a hot day.

6) Removing the fuel lines: (Remember that there may be pressure in the fuel system.) The fuel lines attach under the front left of the tank.  Remove the rear one (that goes to the fuel rail) first.  Remove the front one (that goes to the fuel pressure regulator) next.  Note that if there's any appreciable amount of gas in the tank that the front one will leak gas so put your finger over it when lifting the tank off. (That's why you do that one last.)

7)  Put a rag on the ground to keep from scratching the paint and place the tank against a wall with the front tilted upwards to keep gas from leaking from the front pipe.

8.) Installation is the reverse of removal.  However, here's a few things to note:

- If you don't have the cup then make sure you attach the drain hose to the right rear pipe and that the hose is not kinked when the tank is installed.  If you forget to attach that drain hose then you run the risk of draining gas onto a hot engine block which is generally considered dangerous and a fire hazard.

- Sometimes it's hard to get the tank far enough forward for the posts at the rear of the tank to align with their grommets.  Straddle the bike, sit on it where the seat should be and push the tank forward with your hands at the lower rear corners, being careful not to push the bike off of the center stand.

- Applying some Armor All (or even some spit) to the grommets should help the posts slide down through their grommets more easily.

- To get the posts through the grommets far enough to re-attach the C-clips with needlenose pliers, stand on the side of the bike and lean over the bike with the weight of your stomach on the rear of the tank to push the posts down through the grommets.

- Finally, don't forget to re-attach the fuel tank wiring connector.

edit by scott_ 10-20-13 to replace missing photo
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Offline djaysan

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Re: Removing the gas tank
« Reply #1 on: October 08, 2019, 08:29:13 AM »
Hello, apologies for posting here... I'm not very good at forums :( I searched all the forums for a solution and I partly found it here

I just disconnected my tank and was checking here which one of the two pipes pointing down under the right rear should my orphan line connect to...
Unfortunately I dont see picture here to what the 'cup' is referring to...

Is there a picture that can help? I think there must be a picture :)
  • Poland
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Offline mw074

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Re: Removing the gas tank
« Reply #2 on: October 08, 2019, 09:02:06 AM »
Cup
  • Michigan

Offline djaysan

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Re: Removing the gas tank
« Reply #3 on: October 08, 2019, 09:06:52 AM »
Cup

Don't have this on mine :(

I guess that single line looking at me must be plugged to rear one then? the tank has been painted and both pipes look like they had something attached to it... I don't want to settle a fire  :johnny

sorry for being such a noob
  • Poland
  • F800R, K1100 RS
Proud owner of K1100RS 93' after selling my F800R 11'

Offline Laitch

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Re: Removing the gas tank
« Reply #4 on: October 08, 2019, 09:08:32 AM »
Here's a view from above it. Its outlet can be seen between its two hangers. Attach the hose to it and route the hose to exit behind the right footpeg plate. Otherwise, attach a hose to each of the ports and route them to exit likewise.




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Offline Laitch

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Re: Removing the gas tank
« Reply #5 on: October 08, 2019, 09:12:43 AM »
sorry for being such a noob
Quit being sorry and quit guessing.

One outlet evacuates water accumulating around the fuel cap. The other helps to vent fumes and pressure from the tank. Hook them up one way or the other with vacuum hose of the right diameter and length.
  • Along the Ridley in Vermont.
  • 1995 K75 77,000 miles
I wept because I had no radials until I met a man who had no splines.
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Offline Scott

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Re: Removing the gas tank
« Reply #6 on: October 08, 2019, 10:22:16 AM »
That funnel/cup part is still available for a few dollars, euro's.  Buy one and instal it at some point in the future when the tank is off again.  The two individual lines to the tank are a real struggle to get on the pipes.  I bought one and the next time I have the tank off it's going on.  That will make it real nice.
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Offline volador

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Re: Removing the gas tank
« Reply #7 on: October 08, 2019, 12:04:24 PM »
Forward pipe/tubing stub=Tank vent
Rear pipe/tubing stub=Rain drain of petrol filler cap area
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Offline Soggz

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Re: Removing the gas tank
« Reply #8 on: October 09, 2019, 01:54:01 PM »
Re; rear tank pin locating corclips.
The mighty Chris Harris says to leave em off. If you have a crash, the tank could come off and rip two big holes in it! Fuel onto hot engine... BOOM!
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Offline Martin

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Re: Removing the gas tank
« Reply #9 on: October 09, 2019, 02:38:02 PM »
If you ride a K75s or any Brick that have side covers that hook onto the tank do not leave the "C" clips off. If you hit a decent bump the rear of the tank can jump up releasing the side covers. The releasing of the covers wont happen every time, it is dependant on fuel load, speed, tightness of the rubber grommets and size of the bump. Covers are getting hard to source and expensive, so your call. You've gotta ask yourself do you feel lucky. If you have problem with removing the clips either bend up a piece of coat hanger with a small hook and a finger loop, or attach a cable tie to the clip, or make longer ones out off a piece of sheet metal.
Regards Martin.
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Offline Soggz

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Re: Removing the gas tank
« Reply #10 on: October 09, 2019, 02:55:01 PM »
If you ride a K75s or any Brick that have side covers that hook onto the tank do not leave the "C" clips off. If you hit a decent bump the rear of the tank can jump up releasing the side covers. The releasing of the covers wont happen every time, it is dependant on fuel load, speed, tightness of the rubber grommets and size of the bump. Covers are getting hard to source and expensive, so your call. You've gotta ask yourself do you feel lucky. If you have problem with removing the clips either bend up a piece of coat hanger with a small hook and a finger loop, or attach a cable tie to the clip, or make longer ones out off a piece of sheet metal.
Regards Martin.
mine has the low seat conversion, so no side Panels.
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Offline The Mighty Gryphon

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Re: Removing the gas tank
« Reply #11 on: October 09, 2019, 07:17:55 PM »
Re; rear tank pin locating corclips.
The mighty Chris Harris says to leave em off. If you have a crash, the tank could come off and rip two big holes in it! Fuel onto hot engine... BOOM!

I got rear ended in a crash that totalled the Moby Brick and the KIA that assaulted us.  The tank came off and traveled about 20 feet from the rest of the bike. 

I had the c clips installed on the tank mounts.  They didn't tear holes in the bottom of the tank, rather, the welds that held the mounting pins let go.  Both pins were still in the rubber mounts on the frame.  Despite being very beat up, the tank was still intact after the assault and did not leak any fuel.
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Offline daveson

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Re: Removing the gas tank
« Reply #12 on: October 09, 2019, 07:38:14 PM »
Did you get hurt bad?

Any tips on how to take a fall?
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Offline The Mighty Gryphon

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Re: Removing the gas tank
« Reply #13 on: October 09, 2019, 07:47:13 PM »
Did you get hurt bad?

Any tips on how to take a fall?

Sprained every joint on the riwghtside of my body.

Don't tense up.  Stay loose and roll.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
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Offline daveson

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Re: Removing the gas tank
« Reply #14 on: October 09, 2019, 08:05:20 PM »
Good tip,  hopefully I can do that when it comes to it.

The only time my neck gets tense is when I've been to a chiro,  and they put their hands on your head and say "relax"
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Offline Soggz

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Re: Removing the gas tank
« Reply #15 on: October 10, 2019, 06:56:20 AM »
Evidentially, Chris Harris is a big fat liar,then.
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Offline The Mighty Gryphon

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Re: Removing the gas tank
« Reply #16 on: October 10, 2019, 01:12:51 PM »
Evidentially, Chris Harris is a big fat liar,then.

Not necessarily, maybe he just hasn't had the opportunities that have come my way.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE
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