one of the bubbles in my cb550f tank paint finally ruptured into a full-on pinhole today, thankfully before I rode away on it to lunch. So today I had the pleasure of taping a wad of paper towel over the pinhole so my living room doesn't reek of gas quite so bad. Tomorrow hopefully I'll have the time to call a radiator shop and see if they can just strip the whole thing, MEK the rust out of the inside, and braze any pinholes they find. I'm over preserving the stock paint, I just need a reliable tank on this damn bike. It'll be nice to not worry about what's getting through my petcock / inline filters and messing with my freshly cleaned carbs. Always something...
The problem with "pin hole" rust hoes in gas tanks is that while they might be tiny on the outside, the inside of your tank will look like a moonscape with caters around each "pinhole" which will blow out into a big hole when anyone tries to braze it, I've been there, done that.
MEK (Methyl Ethyl Ketone) won't remove rust, it's a very dangerous chemical which is great for removing moisture, or your eyes, if the fumes come into contact with them, so be careful. Permatex makes a product called Fuel Tank and Radiator repair kit, which I had to use when I discovered a leak in a car's fuel tank a few years ago, it's like a ribbon of grey silly putty that you just knead into a ball and squish into the hole, and once it's dry it'll pretty much stay there until you decide to do something more permanent.
There are a few different fuel tank sealers that'll clean all the rust out of your tank, fill any pinholes, and seal what's left of it against further pinholing. Be prepared to have your bike off the road for a few days while it's curing though, you need to follow the instructions to the letter to make sure it does what it says it will. Cheers, Terry.
