K75s fuel tank leaking!

[cartejo5]

Morning folks, I'm posting on behalf of a pal but will probably end up doing the work.

So what we have is a 1986 k75s which has developed leaks from the low part of the tank at the rear. The paint is all blistered and fuel seeps out, looking on the net it's not unusual to have this problem. Has anyone managed to successfully repair it using for instance JB weld or some other epoxy stuff?

Failing that has anyone got a good fuel tank ideally in Karib blue bmw 618 paint code that they would like to sell, apparently the earlier tanks "his is a 1986 D reg bike" are different but I'm no expert.

Many thanks.

 

[comberjohn]

Epoxy putty will repair your friends tank. I've had to do it on two different K100's that I've owned.
First was an '89 and noticed a smell of fuel and blisters around where the pump sits. Second was an '85 which developed pin holes in the base.
Drain the tank, clean the area thoroughly and use a new packet of putty. Don't use stuff you've had lying around. It goes off.
Any other tank you pick up could be the same as they're about 30 years old now.
I think there was only one type of K75 tank. It was slightly smaller than the K100 which had two different fixings at the rear of the tank depending on whether it was an earlier or later type.

 

[t_s]

I agree with the advice to repair ather than buying a "new" one, which may have the same issues. When it comes to same or different K75 tanks, the K75RT has the same tank that K100s (late ones) have, the K75, K75S and K75C the "flat" standard K75 one.

I've got the advice to repair my leaky rear corner studs with an alloy welding rod called Durafix Google it. Not had the time to use it yeat, but I assume it holds up better against ethanol laced petrol.

Do report back how your repair goes!

 

[Bendy toy]

Have a look at the petrol tank repair options on ww.frost.co.uk http://www.frost.co.uk/por15-motorcycle-fuel-tank-repair-kit.html#product-tabs

I've used Lumiweld rods on aluminium. They work well but its more like soldering so don't expect to do one side and then turn it over and do the other. You also need a big gas burner as alloy rally soaks the heat away. So even if you fill the tank with CO2, the heat required (as opposed to temperature) is probably not suitable on a thin metal tank.