Over the past couple of months I brought an old 71 CT-1 from being a rusting non-running hulk, to being a semi decent looking, safe rider. It still has plenty of patina from the rust I've knocked off, and the interior of the gas tank okay, but the exterior has quite a bit of rust, and chipped paint.

At this point the tank seems to have full integrity, and there are no leaks, and I do not want to repaint it. I'm absolutely fine with the way the bike looks now, but I just don't want that rust advancing and causing a leak.

 So what are the best ways to stabilize the exterior of this? I've seen mention of clear coating the entire thing, but how would I prep it? Or is there another product that could be applied to it on occasion? Or just a heavy paste wax?

 

You use metal etch from a paint store it will leave a zinc phosphate coating that you can paint or clear over. Some metal auto body parts come that way to keep them from rusting 

Would I put zinc phosphate on the entire tank? Would that destroy the paint that is on it? Again, I just want to keep it as is, but try to arrest any more exterior rusting.

I’m looking to do the same with this tank. And I’ve wondered the same thing. So far I just wipe it down with WD40….
 

I've been trying various waxes, even ceramic coating. I decided to try some Howard's feed and wax that I had. It's really designed for wood, has beeswax, carnauba wax, mineral oil and orange oil. I rubbed it all over the tank and let it sit for a while, then buffed it out. It turned the rusty spots darker, which tells me that it might have helped to seal them.

I saw a video of a guy that treats his Rat Rod, that basically has no paint on it, with just boiled linseed oil and something else added to it. It turns it darker, but he claims it retards the rusting.

I'd regularly apply Gibbs Brand Lubricant. 

No you put metal etch only on the rust spots probably use a q tip to apply you can try it on the underside of the tank to see how it works.  Gibbs is good too as I use it also they say you can clear over it but I haven’t tried it 

If I use to Gibbs over the entire tank,  would it affect the paint? My tank doesn't have just chips where it's rusting, there's areas where the paint is rippling from corrosion underneath. However it's been like that for years so it seems fairly stable, I just would like something to seal it

I haven’t tried it on paint maybe MarkT can answer that 

I've used it on painted parts for long periods and I've never had it harm the paint.  You could try a test area to be safe.