Saving a tank WITHOUT lining it?

scott s

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I got this CB350 twin tank from a guy over at the Honda Twins forums. It was a screaming deal; basically just pay shipping. I have $35 in it, plus the cost of a bottle of The Works.

It looks rough, but it's VERY solid. In fact, it was so clean inside that I used a diluted The Works/water soak instead of full strength and rattling around chain, etc. It came out spotless.
BUT..... After about 10 hours of soaking I started noticing water seeping through the Bondo at the top, left front. After draining and rinsing, I chipped off the Bondo and didn't see a thing. The tank is super thick and solid. I chucked up a wire brush in my drill and cleaned a three inch or so circle and found this:




It appears to be leaking at the seam. That little divot in the pic is about the size of a pea or a pencil eraser, or smaller. That's a 4X zoom for the holes.

This tank is so clean inside....I'd really hate to line it. This is right after rinsing. I didn't even finish the process with alcohol, oil, etc., yet.



If.....IF... I have to line it, should I have this dent pulled first? It's about thumb sized and right about where the H in the HONDA badge would be. Everything else on the tank is just a smear of filler away from being ready to prime and bodywork.
I purposely positioned the tank to make the dent appear as bad as possible for the picture.



The tank looks rough in the pics but, again, it's not....it's VERY solid and very straight. And very clean inside.
What's the best approach to sealing up that seam and saving this tank without having to line it?
Also, even though it would mean having to clean it again, I'm thinking about filling it back up with water and letting it sit just so I can see exactly where it's weeping from.



 
I filled the tank back up with water and added green food coloring (because that's what I found in the spice drawer). And the food coloring trick confirmed it. In fact, I buzzed off the Bondo on the other side too and there's a weep there as well. It was holding until I took off the Bondo. Both leaks are at the seam and nearly invisible to the naked eye.
It looks like someone was just going for the "smooth" look on this tank, as the badges and trim strip area is filled in as well.
I still think it can be saved if I can find someone to braise/solder it.
 
On my 72 CL100 resto the tank turned out to be swiss cheese. I took it to local radiator shop. They soldered it up for $60 next day. Not real pretty but its on the bottom so not really noticeable, unless your on the ground looking up under it.

I went ahead and sealed it w por15 later. Just for good measure.

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I've had excellent results with POR15, even sealing holes I could see daylight through. I have no doubt that would probably stop these leaks, but..... DAYUM, the tank is so clean inside!! There's just something wrong with sealing a tank this clean!!
 
hillsy said:
If it was me and they are the only holes I would solder them.

And then seal it too.
I was in the same situation as you. Super clean tank inside but had some pin holes along the seams. Had the holes welded up and I sealed the tank anyways. The last thing I wanted was to ruin my $800 paint job because of a new seam drip that developed over time. Seal it and be done. Unless you don't mind ruining all that hard work when a new hole shows up. I always use caswell and it has never failed.
 
sbaugz said:
And then seal it too.
I was in the same situation as you. Super clean tank inside but had some pin holes along the seams. Had the holes welded up and I sealed the tank anyways. The last thing I wanted was to ruin my $800 paint job because of a new seam drip that developed over time. Seal it and be done. Unless you don't mind ruining all that hard work when a new hole shows up. I always use caswell and it has never failed.

Yep. I last used the caswell liner (clear) and it worked great. Could still see the clean metal in the tank but was worth it to me to have the metal preserved in there. I'm a fan of no liner where possible also, but if theres a pinhole leak, it will cause grief down the road.
 
What can happen between a liner can also speed up the rotting process and that paint will fail just the same, I may try to use a smaller tip and silver solder along with a flux paste brushed on the entire seam then slowly work just the very edge drawing the solder into any split or gap sorta like tinning the entire edge.

Bad liner:
 

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Looks like another bad Kreem liner. I hate Kreem. I've seen ONE that was successful.
 
scott s said:
Looks like another bad Kreem liner. I hate Kreem. I've seen ONE that was successful.

Not sure what it is, but if your gonna use a coating of any sort, the prep work needs to be as good as any exterior paint prep.
 
I hear that a lot about Kreem, but I've done all 3 of my bikes with it. One has had it in there for 18 years. Another for 12-13 years and the other for 4 or 5 years. Wondering why it fails on people?
 
After blasting:
 

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Damn Tuna! that is probably the best way to deal with rust/holes, but holy crap thats a lot of work.

ive sealed two gas tanks with the caswell liner and have had no complaints. you really do need to prep well and i think that's why so many liners fail; user error.
 
doc_rot said:
Damn Tuna! that is probably the best way to deal with rust/holes, but holy crap thats a lot of work.

ive sealed two gas tanks with the caswell liner and have had no complaints. you really do need to prep well and i think that's why so many liners fail; user error.

Idle hands mang.
 
I took the tank from my GL1000 to a local radiator shop when I found a pin hole leak in it. They soldered up the leak, finished cleaning the inside, lined it with Redkote and painted the outside. They charged me $150. I feel like it was money well spent, it's a 40 year old tank. I doubt I'll ever have to worry about it again.
 
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