1995 K75 leaking tank.

[143143]

1995 K75 leaking tank.
I'm thinking of purchasing a 1995 K75 with only 16,000 miles on it. Unfortunately the paint is peeling off underneath where the seem is. This is what the owner is telling me. He say's it's because the ethanol has separated it he gas and the vapors have cause damage. Any opinions on what could be happening and on a bike that has been sitting to long? Thanks. Sincerely Ted....

 

[acejones]

1995 K75 leaking tank.
I'm thinking of purchasing a 1995 K75 with only 16,000 miles on it. Unfortunately the paint is peeling off underneath where the seem is. This is what the owner is telling me. He say's it's because the ethanol has separated it he gas and the vapors have cause damage. Any opinions on what could be happening and on a bike that has been sitting to long? Thanks. Sincerely Ted....

O ring seal in the bottom of the tank is leaking. Remove tank, replace seal, reinstall tank, go ride. ( most likely scenario)
Be careful, the tank is aluminum.

 

[lkchris]

Water in fuel = corrosion = hole in tank. It's happened before.

 

[jforgo]

I had pinholes in a steel tank - POR15 sealed them

 

[acejones]

Whatever it is, you have to take the tank off anyway. I'll still bet on the O ring.

 

[32232]

Water corrosion may mildly discolour the aluminum K75 tank, but it won't perforate it. Odds on the leak is at the O ring.

 

[35634]

Water collects in the lowest part of the tank and will corrode through the aluminum. And bubble the paint. On old K's check the bottom seam on the sides about 1/3 back from the front of the tank. On the K75s & rt this point is hidden by the fairing. Many use JB Weld to seal it, or 2 part epoxy gas tank sealer.

 

[98lee]

Whatever it is, you have to take the tank off anyway. I'll still bet on the O ring.

I'll take that bet with you and Dave. Two beers at the Rally?

The O- ring on k75s virtually never leak unless they have been taken apart, while it is quite common for the tank to corrode through (especially on the left side seam just to the rear of the fuel pump) if the bike has been sitting for years with bad fuel in it.

 

[143143]

O ring seal in the bottom of the tank is leaking. Remove tank, replace seal, reinstall tank, go ride. ( most likely scenario)
Be careful, the tank is aluminum.

Thanks Bro. Sounds like an easy fix.

 

[143143]

If the tank has corroded can it be fixed?

 

[98lee]

Let us know if he was right (I REALLY doubt it).

 

[98lee]

If the tank has corroded can it be fixed?

Some people trust epoxy type fixes. I prefer to replace the tank with a good used one. Remember the leak is directly above the header.

 

[cycleman2]

If the tank has corroded can it be fixed?

Steel tanks can be brazed or soldered ( similar to a leaking rad ) but I would think an alum. tank would have to be welded and then sealed with any one of the aftermarket product's out there. Lots won't weld a gas tank.

You should price the bike accordingly and included the purchase of a used tank, painting etc. Always look at these types of things when buying a used bike as a deal breaker unless you can more than cover the cost of the replacement tank. If the bike has been sitting so long the tank has been eaten through, then you are going to dump more money into the rest of the bike to get it running properly.

Its always a better deal to find a bike in better condition as you can dump $ 2000. into any of these old BMW's pretty quickly ( even if you are doing all the work ). If at the end you get the bike for a better price and then it turned out to be an O ring, well that's OK and you have another story to tell.

 

[98lee]

I'm moving this thread to "Flying Bricks" as it is about early Ks.

Head and arms inside the ride please. Here we go!

 

[pglaves]

Water corrosion may mildly discolour the aluminum K75 tank, but it won't perforate it. Odds on the leak is at the O ring.

Some people trust epoxy type fixes. I prefer to replace the tank with a good used one. Remember the leak is directly above the header.

I have had to repair three of the K75 tanks where corrosion had caused a hole - yes a hole, not discoloration - which caused the tank to leak. They were all at the low point where water will settle in the bottom of the tank.

I have had good luck with "Gas Tank Sealer" purchased at the auto parts store; the kind that comes in an epoxy stick like a little corn dog where you slice off a piece and knead it to a uniform color. On two of the tanks the hole was inside (toward the center of the bike) of the seam so the repair was not ordinarily visible unless a person was lying on the ground beside the bike. On the third bike the holes were on both sides of the seam so the repair could be seen by a sharp set of critical eyes even with the repair painted to sort of match.

Surface prep started with a wire brush in a Dremel tool to remove loose paint and aluminum oxide. This was followed with light scuffing with emory cloth down to bare metal.

The instructions said it would stick on corroded metal wet with gas but I decided a bit more effort was in order. As far as I know all three repairs are still sound several years later.

 

[Rudyjo]

The pin-hole leak on my 92 K75RT fixed with JB Weld has held up for three years now, I would not hesitate to use it again.

 

[k100lt]

The pin hole leak on my 1989 K100LT fixed with JB Weld has held up for 10 years with no problems. Good stuff!