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Discussion Starter #1
Hey guys,

71 CB 350

I searched the posts for gas tank holes and repairs, but they were all rust related, and my problem is that the underside of my tank has "crinkles" to it - which is weird because aside from a few dents in the tank it's not like it was smashed and straightened.

I do have a 2nd tank, and it has crinkles too, although not as bad. Is it possible these "crinkles" are out of the factory? It seems really unlikely.

Anyway, the problem is that it looks like the crinkle under the tank has been in contact with the sharp ridge of the top of the frame and vibration has buzzed a hole in the tank. It weeps fuel when I fill the tank more than half way and my garage smells like it's about to ignite.

I tried cleaning it up and using JB Weld to bond the hole, and I took a grinder and removed the ridge-tang from the frame where that crinkle is, but it's weeping again.

Any suggestions on how to best repair this single hole? I don't like the idea of brazing or welding, as I've never liked the notion of blowing myself up. Or should I scrap the idea and go with my other gas tank?

I have a 2nd tank that I am stripping down but I like the one I have now, it has a beaten patina that I like (I bought the bike with the tank stripped down to bare steel and was planning on painting it, but the more I look at it the more I like it, and am going to keep it bare metal - I keep it clean with fine grit sandpaper and keep Honda polish on it, and surprisingly it does not rust over even here in GA).



CB 350 Close.jpg
gas tanks.jpg
gas tank hole.jpg
 

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Have a radiator shop solder it.
 

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Sensei
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IF your tank was in contact with the frame, it was likely improperly mounted...
Usually, the culprit is a lack of, or partial, or damaged rubber support cushion at the rear of the tank.....

Were it mine, I'd fill it with dry ice chunks and let it sit upside-down with the gas cap closed, petcock removed, and crossover hose off for a couple hours and then braze the hole shut......
The heavier CO2 will displace any remaining gas fumes and it is a fire extinguishing agent as well as non-flammable itself......
 

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IF your tank was in contact with the frame, it was likely improperly mounted...
Usually, the culprit is a lack of, or partial, or damaged rubber support cushion at the rear of the tank.....

Were it mine, I'd fill it with dry ice chunks and let it sit upside-down with the gas cap closed, petcock removed, and crossover hose off for a couple hours and then braze the hole shut......
The heavier CO2 will displace any remaining gas fumes and it is a fire extinguishing agent as well as non-flammable itself......
We employed a similar method with car gas tanks back in the day except we would run a car's exhaust into the filler neck for about an hour. Dry ice seems like a lot better idea with less setup.
 

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You need to use a dedicated gas tank epoxy putty.
https://wanaryd.com/permatex-gas-tank-repair-patch-epoxy-12020.html

This stuff will outlast the tank. I've used it on rusty tanks that were cleaned as best as possible and also filler pipes that were rusted out. Just did the neighbors 05 escape with the tank on the vehicle.

Warm it up before kneading it and knead it well, it has a long set up time compared to the fast epoxy. Place a bigger patch than just the leaking area. Oh and wear gloves.
 

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Last time I was in the local radiator shop they told me they dont weld radiators any more but use an epoxy that better than welding. You might check with with your local shop.

Bill
 

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I'm on the "epoxy" bandwagon in this one..used it on other stuff. Heat / solder has its place, hell.. they are literally "gluing" quater panels to cars now. And the metal will tear before that epoxy lets go.. plus NO HEAT!
 

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I used the kneadable epoxy to fix a plastic gas can that had a puncture in it. I tried saving it as these newer style cans with the spring-loaded spouts seem to cause me to lose more gasoline than the older ones of years back.
 

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The krinkles you describe are from the forming of the sheet metal. I'm sure Auntie Honda didn't care too much for the appearance of the underside of the tanks. Take the ball end of a ball peen hammer and pound a dent into the damage area. Then fill it with the epoxy of your choice. Make sure the epoxy is thick enough to give it some structure.The tank on my 450 had some pinholes from weld repairs. I used Caswell liner on it and it solved the problem. This is the fourth season so far. I liked the results from the Caswell liner so much that I do it to all my bikes now.
 
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