Add me to the cracked fuel tank list

[Snowy]

Just to add another level to the cracked tank saga.

On an outing recently I noticed a large build up of clay on top of the swing arm. It was gradually drying and it had a very definite imprint of the underside of the fuel tank in it.

When bottomed out, ie all the shock stroke is used, the swingarm appears to come within approx 20mm of the underside of the fuel cell.

So, if the clay dries, and then I bottom.....what happens?

If small rocks are present in the clay and I bottom?


In my humble experience, if it CAN happen....it eventually will.

[JRWooden]

Just a note... there is a cracked tank poll running HERE:

http://f800riders.org/forum/showthre...s-tank-cracked

... and while not scientific, and likely overloaded with USA-riders
it still makes you suspect there is something different about the Canister-equipted bikes,
or the environment the operate in that causes cracking...................

[westcoaster9]

Originally Posted by Westy99

When mine was replaced, they had to order one from the Motherland, we'll see how it holds up. I believe it was the newer part number.

Small correct here or "Achtung"
--in Germany it's the Fatherland

[Westy99]

Originally Posted by westcoaster9

Small correct here or "Achtung"
--in Germany it's the Fatherland

Either way it took a month.

[westcoaster9]

Getting back to the subject matter, cracked gas tanks, lets look at alternative solutions to warranted replacement like to 2 part epoxy used for plastic bumper repairs--or marine epoxy B52 --or J P Weld --or Bondo -or-or -etc.
Who has tried what and has it help up.

Paying $1000 to have the dealer replace the tank is certainly not going to be my first option--how about you?

[ebrabaek]

Originally Posted by westcoaster9

Getting back to the subject matter, cracked gas tanks, lets look at alternative solutions to warranted replacement like to 2 part epoxy used for plastic bumper repairs--or marine epoxy B52 --or J P Weld --or Bondo -or-or -etc.
Who has tried what and has it help up.

Paying $1000 to have the dealer replace the tank is certainly not going to be my first option--how about you?

When Mine cracks..... I will make my own out of Carbon fiber.....and special epoxy. Might even squeeze out another gallon....he-he.... It is only the outer shell that is cracking.... so I would imagine many will just continue to ride with it cracked.....

Erling

[westcoaster9]

Originally Posted by ebrabaek

When Mine cracks..... I will make my own out of Carbon fiber.....and special epoxy. Might even squeeze out another gallon....he-he.... It is only the outer shell that is cracking.... so I would imagine many will just continue to ride with it cracked.....

Erling

Dear Ebrabaek,
Seriously here, if you have the molding skills and epoxy knowledge to make your own tank you are certainly knowledgeable enough to comment on the best patch/calking epoxy based repair product to use---
Please share you vast knowledge here as there is many of us that don't have your education in plastics.
My approach would be to take a die grinder, chuck up a fine tipped steel router and cut a v-notch in the outer shell along the crack outline.-- lets say 1.5 to 2mm deep. Then take some of the fine plastic material routed out and test the epoxy to see if it dissolves the parent material. This should indicate it will bite into the cracked edge and hold up.
Now old chap-- please critique this approach with your vast background here.
Old Blue

[ebrabaek]

Originally Posted by westcoaster9

Dear Ebrabaek,
Seriously here, if you have the molding skills and epoxy knowledge to make your own tank you are certainly knowledgeable enough to comment on the best patch/calking epoxy based repair product to use---
Please share you vast knowledge here as there is many of us that don't have your education in plastics.
My approach would be to take a die grinder, chuck up a fine tipped steel router and cut a v-notch in the outer shell along the crack outline.-- lets say 1.5 to 2mm deep. Then take some of the fine plastic material routed out and test the epoxy to see if it dissolves the parent material. This should indicate it will bite into the cracked edge and hold up.
Now old chap-- please critique this approach with your vast background here.
Old Blue

No epoxy will dissolve the polywhatever... ( tank)... but if you use poluester resin..... some might. The trick is first try to find out the chemical structure of the cracked tank, as there are a lot of different composites used nowadays. Some cannot be fused once cured. Epoxy will stick to just about anything....but again some polymers are inherently " sticky" and nothing except the proper glue will bond them. This is what I would do. Try to find out what native bonding material that would work. That would incorporate a call to the tank manufacture, and they might not release that information. So most likely I would proceed with the following..... Try different epoxy's... (I usually stock 6-8 different types).... after mixing each..... "spill" a drip on the tank exteriour after cleaning, and wiping with acetone. After cured...take a sharp knife.... simply try to pry off the "drips" see which one stick the best... When you find one that works.... you'l know... it simply wont come off. Then try to clean the area to be patched...with isopropyl alchohol....then acetone.... Mix the winning epoxy.....add some very fine cut strands of Carbon fiber for color and added strength...... carefully fill the crack...... perhaps taping off the area with aluminum tape...... then cure....sand.... your done.....This is assuming that the cracks are only in the outside tank, and the inside is not breached. If it is... Make a hole tank, as it would be impossible to fix it through the outer layer......

Erling

[westcoaster9]

Originally Posted by ebrabaek

No epoxy will dissolve the polywhatever... ( tank)... but if you use poluester resin..... some might. The trick is first try to find out the chemical structure of the cracked tank, as there are a lot of different composites used nowadays. Some cannot be fused once cured. Epoxy will stick to just about anything....but again some polymers are inherently " sticky" and nothing except the proper glue will bond them. This is what I would do. Try to find out what native bonding material that would work. That would incorporate a call to the tank manufacture, and they might not release that information. So most likely I would proceed with the following..... Try different epoxy's... (I usually stock 6-8 different types).... after mixing each..... "spill" a drip on the tank exteriour after cleaning, and wiping with acetone. After cured...take a sharp knife.... simply try to pry off the "drips" see which one stick the best... When you find one that works.... you'l know... it simply wont come off. Then try to clean the area to be patched...with isopropyl alchohol....then acetone.... Mix the winning epoxy.....add some very fine cut strands of Carbon fiber for color and added strength...... carefully fill the crack...... perhaps taping off the area with aluminum tape...... then cure....sand.... your done.....This is assuming that the cracks are only in the outside tank, and the inside is not breached. If it is... Make a hole tank, as it would be impossible to fix it through the outer layer......

Erling

Thanks much for that well outlined approach. Questions arising from above. Why aluminum tape? As the seam of the crack is always dry I must assume its not leaking Further, some threads back somebody said that a dealer had replaced his tank and the old tank was cut open to show its a laminate construction made with an inner fuel bladder and and outer decorative shell, which is where the cracking takes place.

[ebrabaek]

Originally Posted by westcoaster9

Thanks much for that well outlined approach. Questions arising from above. Why aluminum tape? As the seam of the crack is always dry I must assume its not leaking Further, some threads back somebody said that a dealer had replaced his tank and the old tank was cut open to show its a laminate construction made with an inner fuel bladder and and outer decorative shell, which is where the cracking takes place.

Absolutely...... I usually use aluminum tape to mask.....as regular paint tape get's saturated by the epoxy, and can be a mess to remove....as they do not offer a good barrier. But in reality... what ever you have on hand will do.

Erling

[westcoaster9]

Originally Posted by ebrabaek

Absolutely...... I usually use aluminum tape to mask.....as regular paint tape get's saturated by the epoxy, and can be a mess to remove....as they do not offer a good barrier. But in reality... what ever you have on hand will do.

Erling

Now you have helped me and others with an approach that may work-- my fear is if BMW starts a "good will replacement" will I qualify with a patch job unless it's leaking? Of course nobody can help me with this question except BMW--and they of course will sit in the weeds until a tank fails and kills someone.
Their shaft drive issue on BMW's would fill a book and their answer is, 'there are only limited failures of this part"

[ebrabaek]

Originally Posted by westcoaster9

Now you have helped me and others with an approach that may work-- my fear is if BMW starts a "good will replacement" will I qualify with a patch job unless it's leaking? Of course nobody can help me with this question except BMW--and they of course will sit in the weeds until a tank fails and kills someone.
Their shaft drive issue on BMW's would fill a book and their answer is, 'there are only limited failures of this part"

I know...this is one of many. I have an '09...with just over 10000 miles on it.... Very hot desert southwest....many days over 100 F each year..... I have looked for cracks.... Not a thing... Go figure.....

Erling

[JRWooden]

Originally Posted by JRWooden

John:
Yes, I'm with you, I waited till my 3-yr factory warranty was almost expired then had them replace the tank...
From the looks of things it will be "well" cracked again within 2-years as it already has tell-tail signs of a a crack starting now after only 3 months in use... Hopefully they will have a good design fix inside of 2-years.........

I was told by the parts guy at the local dealership today that he "thinks" (not 100% sure) but thinks that if a part is replaced by BMW as a warranty repair that you do NOT get the 2-year part warranty. Since it was a warranty repair the replacement/warranty part is only warranted for the rest of the factory warranty ... if true this shoots my plan all to hell...


Anybody know for sure?

[ebrabaek]

Originally Posted by JRWooden

I was told by the parts guy at the local dealership today that he "thinks" (not 100% sure) but thinks that if a part is replaced by BMW as a warranty repair that you do NOT get the 2-year part warranty. Since it was a warranty repair the replacement/warranty part is only warranted for the rest of the factory warranty ... if true this shoots my plan all to hell...


Anybody know for sure?

My local dealership in New Mexico stated specifically the 2 years applies. On the second go on the valve cover gasket..... I got the new kit with shorter bolts...., and they mentioned that I had 2 years.....even though I'm out of the factory bike warranty...

[JRWooden]

Originally Posted by ebrabaek

My local dealership in New Mexico stated specifically the 2 years applies. On the second go on the valve cover gasket..... I got the new kit with shorter bolts...., and they mentioned that I had 2 years.....even though I'm out of the factory bike warranty...

Thanks that gives me some hope!
I'll fight the good fight in about another year or so ..............