3 Re: Fuel Tank Leaking Mon Sep 05, 2022 6:53 pm
Laitch
Life time member
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1995 K75 90,000 miles
4 Re: Fuel Tank Leaking Mon Sep 05, 2022 6:55 pm
Rick G
admin
That picture is of the early type you will find the correct O-ring from 86 onward. I cant recall the size but Real OEM will give you the size.
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"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived." Dalai Lama
Bikes 1999 K1100 LT with a Big Block 1200
5 Re: Fuel Tank Leaking Sat Sep 10, 2022 12:58 pm
robmack
Life time member
RealOEM doesn't list the size of the O-ring that seals the fuel sender unit. I checked the Canadian price for the original BMW part and BMW want $23.00 plus HST. For an O-ring!! Highway robbery!
As far as I can tell, the correct size metric O-ring should be 4.5x45. That has a cross-section of 4.5mm, OD of 54mm and ID of 45mm. This is eye-balling it; can anyone else confirm?
As far as I can tell, the correct size metric O-ring should be 4.5x45. That has a cross-section of 4.5mm, OD of 54mm and ID of 45mm. This is eye-balling it; can anyone else confirm?
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Robert
1987 K75 @k75retro.blogspot.ca
6 Re: Fuel Tank Leaking Sat Sep 10, 2022 2:38 pm
Laitch
Life time member
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1995 K75 90,000 miles
7 Re: Fuel Tank Leaking Sat Sep 10, 2022 3:24 pm
8 Re: Fuel Tank Leaking Sat Sep 10, 2022 4:52 pm
duck
Life time member
There's no spec for that torque in the BMW manual. Just get them nice and tight.
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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
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9 Re: Fuel Tank Leaking Sat Sep 10, 2022 5:51 pm
robmack
Life time member
Laitch wrote:Euro Motoelectrics confirms.
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Robert
1987 K75 @k75retro.blogspot.ca
10 Re: Fuel Tank Leaking Sat Sep 10, 2022 6:37 pm
robmack
Life time member
FYI: Found a good source for these O-rings on Aliexpress. 5.0mm CS instead of 4.5mm, but they are Vitron which is good if you're using E10 fuel.
Search for this title "CS 5mm OD16-100mm Green FKM Fluorine Rubber O Ring O-Ring Oil Sealing Gasket" to get to the product. If I posted a link, it would probably be broken in a couple months.
UPDATE: Received the o-rings from Aliexpress in the mail. They fit perfectly and the slightly extra thickness helps to seal a little better than an OEM o-ring (5mm versus 4.5mm).
Search for this title "CS 5mm OD16-100mm Green FKM Fluorine Rubber O Ring O-Ring Oil Sealing Gasket" to get to the product. If I posted a link, it would probably be broken in a couple months.
UPDATE: Received the o-rings from Aliexpress in the mail. They fit perfectly and the slightly extra thickness helps to seal a little better than an OEM o-ring (5mm versus 4.5mm).
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Robert
1987 K75 @k75retro.blogspot.ca
11 Re: Fuel Tank Leaking Tue Aug 08, 2023 11:35 am
taube
active member
Having the same issue as the OP
My tank is leaking from this plate, so I ordered the replacement o-ring from EuroMotoElectrics.
I also found the FKM Viton O-Rings robmack mentioned on Aliexpress, so I've ordered '55mm OD x 5mm thickness'. Yes I'm buying a redundant part, but it's very cheap, and AliExpress takes ages to ship anyway.
My tank is leaking from this plate, so I ordered the replacement o-ring from EuroMotoElectrics.
I also found the FKM Viton O-Rings robmack mentioned on Aliexpress, so I've ordered '55mm OD x 5mm thickness'. Yes I'm buying a redundant part, but it's very cheap, and AliExpress takes ages to ship anyway.
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Restoration project: 1988 BMW K100RS
Currently riding: 2019 Honda CBR300R
12 Re: Fuel Tank Leaking Tue Aug 08, 2023 2:10 pm
Point-Seven-five
Life time member
I get my o-rings at the industrial bearing shop. Viton for about $3. They have them in stock, no waiting. You should find your local shop. Good prices on bearings, too.
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Present: 1991 K100RS "Moby Brick Too"
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
13 Re: Fuel Tank Leaking Tue Aug 08, 2023 3:01 pm
IainM
active member
I had the same leak from the fuel sensor plate which was easily fixed by cleaning the mating surfaces and replacing the O-ring. It has been fine since and this was ~ 5 years ago.
Iain
Iain
14 Re: Fuel Tank Leaking Sun Aug 13, 2023 2:20 am
taube
active member
Alright, I replaced the o-ring and it stopped the leak from my fuel level float plate.
As Iain noted, cleaning the mating surfaces helped tremendously. My sender
unit accumulated a lot of rust... I think the old o-ring might have been fine, but it could no longer seal after being disturbed because the surface was so rough. Photo is before a WD-40 and wire brush treatment.
As Iain noted, cleaning the mating surfaces helped tremendously. My sender
unit accumulated a lot of rust... I think the old o-ring might have been fine, but it could no longer seal after being disturbed because the surface was so rough. Photo is before a WD-40 and wire brush treatment.
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Restoration project: 1988 BMW K100RS
Currently riding: 2019 Honda CBR300R
15 Re: Fuel Tank Leaking Sun Aug 13, 2023 2:30 am
bad boy
Life time member
taube
looks like your K needs quite a bit of TLC
I wish you lots of success
looks like your K needs quite a bit of TLC
I wish you lots of success
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Cheerz, David
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1997 Peraves Super Ecomobile: a Kevlar reinforced monocoque with outrigger wheels, seating two.
K75 fork, K100 monolever, headlight, indicators, K1100RS gearbox, K1200RS 589 instrument cluster, engine, rear wheel
K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » Fuel Tank Leaking
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