BMW K bikes (Bricks)

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K100Sprint

K100Sprint
active member
active member
Came out this AM and opened the garage door to the overwhelming smell of petrol. A quick check showed nothing around the lines/injectors/throttle bodies ... but a closer inspection along the bottom edge of the tank (partially obscured by the fairing) revealed this:

Sooooo, I think I know why my Brick was such a "good deal" Tank_l10

I don't know if you can make it out, but it looks like the P.O. put some kind of putty or adhesive over the spot to hide the leak when I picked it up. Unfortunately, if he blows off my email and calls to "make it right" I am stuck, as this was an "as is, where is" sale and there is no lemon law on private transactions.

Anybody got an idea how much a tank repair would be? Or if not, what do you think a used tank should run for an '85?

Thanks forum brothers and sisters!

Paddy


__________________________________________________
May the road rise to meet you ... and may gas prices drop substantially.

1985 K100 w/ Sprint fairing
Member BMWMOA #64178
Member GNBMWR #118
    

sidecar paul

sidecar paul
Life time member
Life time member
Don't be too despondent K100Sprint, leaks, particularly around the lowest section where the fuel pump sits, are quite common.

Both my K's have been fixed with 'JB weld', and it's held for more than 15 years in both cases. There are many 'fixes' on here so try the search facility. I seem to recall some members having success with Permatex products.

Good luck,
Paul.


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'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015) 
....No CARS never ever!
    

robmack

robmack
Life time member
Life time member


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Comberjohn

Comberjohn
Life time member
Life time member
Very common. Had it on both my K's.
Epoxy putty is a pretty good fix. Especially if you can hide it in behind the fairing and that's usually where they go. As Paul says, near the fuel pump. Use new putty each time. It goes off after a while.
Although my '84 developed pin holes in the base.
They usually blister first. My '89 went into a 3mm hole when I poked the blister.
I would try to repair the original tank. Even much younger tanks could be the same.


__________________________________________________
Life is not a rehearsal.
2010 VFR 1200F DCT 
2010 R1200GS(gone)
1986 K100 Silver(gone)
2012 K1600GT(gone)
1984 K100RT Madison Silver(gone)
1989 K100LT Stratus Grey(gone)
1984 K100 Red(gone)
http://www.johnsdrivingschool.co
    

Crazy Frog

Crazy Frog
admin
admin
From what I can understand, over the years you always get a tiny little bit of water mixed with the gas or entering the gas tank when it's raining and you open the gas cap.
Water being heavier than gas, it seats a the lowest point of the tank and slowly corrodes the aluminum.
As a preventative maintenance, every 2 years, I empty my tanks and clean them.
The seam where K100spring has a leak is very common.
My advise is when you repair the leak, spread whatever repair product you use way over the pin hole.

Quick temporary fix:
Take a bar of soap and shave little pieces out of it. take a piece of bread,  a bit of water and start to mix the bread and soap to get a sticky paste. Stick it on the leak and voila....
I spent 6 months in Africa with a big gash in my jeep's gas tank that was 'repaired' with this solution.
IT WORKS!!

CF


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Sooooo, I think I know why my Brick was such a "good deal" Frog15Sooooo, I think I know why my Brick was such a "good deal" Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

RT

RT
Life time member
Life time member
No sweat. Permatex make a kit that you can use without having to dry out your tank. I've used it (twice as I was stingy with the patch first up) So far, 2 years with no problems. My patch was black stuff, doesn't look so good if I ever upended my bike.


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2011 R1200RT
    

RicK G

RicK G
admin
admin


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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 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Did anyone ever hear of or try a repair with this stuff.  In the video they repair a hole in a soda can.  Downside is that you will need to do a paint job when you're done.  Interesting stuff.

http://durafix.com/index.html


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

the.postman

avatar
Life time member
Life time member
I'd deff. try any repair from the out side (patch) first before you resort to any method of lining from the inside, like the POR15 robmack mentioned. If the lining method dosn't work its a real bugger to remove for a second go, unlike the patch from the outside (permatex)


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1985 K100 RS   104EA49840092        #0081788     SILVERish (Madison) Prod. date 05/12/84
1984 srx 600
1986 cbr1000f/h
    

VashonK100

VashonK100
active member
active member
I had the same issue, pinholes in the corner of the tank.  I widened them up a tiny bit, got rid of any soft edges, Used JB weld and then did Red Kote inside.  Still putting the bike back together and hoping it holds.

http://www.strangelife.com
    

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