So, while gathering parts to do the crank seals on my DT360, I also picked up a sweet little AT3. It had what looked like varnish on the outside of the tank, down by the seam on the left bottom. I picked at it and sure enough, it started leaking gas. I drained it, and found some pinhole leaks down there, and just went ahead and ordered the tank kit from POR15. followed the instructions exactly, and let it cure for 96 hours. put it back on, and long story short-it still has fuel weeping out somewhere in that same area. I discovered it late in the day yesterday and never really got to investigate closely, but I have a classified ad here looking for a replacement tank to use while I figure out what to do about my original one. I will use any year tank that fits and doesn't leak temporarily until I get this one fixed, or just get another that does not leak, and paint it (maybe) anyone got any thoughts? Can I do another POR 15 coat over this "new" treatment?

If the original prep for POR15 wasn't done thoroughly, a second coat would be a waste of time and money, in my opinion. I have used POR15 to seal up tanks that have bigger than just pinholes, and they are still going strong. I do vinegar wash, evaporust, then the marine clean the por15 comes with, and it's important to swoosh the sealer around slowly to make sure you get a nice thick layer everywhere. Regardless though, bummer, hope you can get it fixed up!!

The thing is, the tank was pretty clean inside and i did clean, etch and dry the tank thoroughly before I applied the sealer. I rolled that thing around for half an hour before I poured out the excess. Some sealer weeped out of the pin holes but sealed up as far as I can tell. I need to remove it and inspect, but I think i prepped it well. My inly thought is that the very lowest point of the seam may have not gotten clean or touched during the cleaning part of the prep. But no screw nut bolt chain or bb is going to touch that very small area. 

POR15 has always worked for me...  though I avoid using sealer unless there is absolutely no other option. 

First exposure to the product was helping a friend.  He "went through the steps" but had a fail due to the tank not being clean enough...  varnish/sludge from old gas. 

I learned from that mistake that tank prep is a lot like carb cleaning on these old bikes...  sometimes the first (or even second) attempt isn't enough...  even if you soak a carb in Berryman's overnight and blow out all the passages with high pressure air...  there are times when it will NOT get the carb clean enough even though it appears to be clean. 

So every tank I've done, I've gone way overkill on the cleaning.  The most difficult are the ones that "look pretty clean"!  Rust in a tank sort of takes care of the gas deposits for you.   I've spent hours and hours cleaning it over and over before using the kit.   The "etch" will not remove varnish... and I'm not sure the cleaner does that well either. 

Ironically, the best thing I've found for the first step in cleaning is Ethanol.  If you have E85 (up to 85% ethanol) at a gas station near you, it works great at dissolving and removing even rock-hard fuel deposits if you let it sit for a week.  This might mean submerging the tank in a tub or something if it has pinholes. 

I will look though my tanks and see if I have something decent...  tanks from the 72-73 125 or 175 should be an exact fit except for paint color. 

If you had a tank Mark, that would be awesome! Would be happy with any color, or even an MX tank, just so i could ride it!  I looked on ebay, and the few tanks on there are the bottom of the barrel, talking rust inside and out, just terrible. I really appreciate your sound advice and offer to look through your stash for something I could use. 

MarkT =  MarkTank 

He just recently helped me out with a good solid tank to replace one that I tried double coating. The double coat lasted about 6 months or so. Same as you, it was leaking thru the seamed edge. I’m about to do some bodywork and touch up paint on the MarkTank to make it look a little better without doing a complete repaint and decal kit. Good luck!

We used to get the radiator shop to solder them up.

The only 2 I have of that style have rust.  I don't know how bad it is.  One is much worse than the other.  I don't have any evaporust or I'd dunk the better one and see what happens.  Shipping costs would probably be about $30 if you want to take a chance.  PM me your email if you want pics.

well, thank you for looking. I called POR15 and talked to them about my tank. I ordered another small can of sealer and am going to try a fiberglass reinforced patch on the outside. wish me luck!

I lined the inside of a really nice tank that simply let loose with pin holes along the bottom surface of one side. The holes were pretty large, so I applied aluminum tape across that surface before I lined the tank. I originally planned to peel off the tape once the liner cured but I decided to leave it in place since it is not in clear view. It has held up well so far and that was done back in July of 23.

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