Phil Wood Tenacious Oil is the magic sauce for freewheels. And, yeah, if it's still sticky tomorrow, then you were on the right track and just need to give it a fully-submerged soak in a better solvent than WD-40.

If you really want it to be clean inside, after an overnight soak in mineral spirits, get a junk saucepan, fill it full of water and boil the sucker for half an hour or so. You'll be amazed how much nast floats to the top. (Which is why you don't wanna use a good pan.) Fish it out with tongs while the water is still boiling, let it drip out, then set it on a crappy towel to dry. (Which it will, almost instantly, down to the last little crevices and gaps, since the water that's still in it is just under boiling temperature.) Then run the Tenacious Oil into it while it's still warm.

--Shannon

PS: I learned the "just boil the sucker" trick from shooting (and cleaning) black powder revolvers. The residue gets everywhere, and it's hygroscopic, and it forms sulfuric acid when it combines with the water that it sucks out of the air... it would probably rust dirt, given what it does to steel in a day or two. The only other option was to completely disassemble the action, because of all the little springs and screws and stuff... sound familiar? I'd also heat the whole thing in a 350 oven for about 10 minutes, and then wipe it down with gun oil while it was hot. Like seasoning a cast iron frying pan, it opens up the surface pores in the metal a little bit, so they grab the oil when the metal cools and shrinks. I shot those guns for years, and never had a speck of rust. (But I don't recommend putting your freewheel in the oven.)

You won’t use WD40 because it is ”weird and waxy” but you’ll use automatic transmission fluid which contains all kinds of extra additives and is meant to be used in a sealed unit. ATF and motor oil were never designed to be used in open air systems.

WD40 isn’t weird and waxy. It is just solvent with mineral oil in it. The mineral oil is in the same class and of a similar composition to the oil used in TriFlow, 3-in-One oil, or any commercial light mineral oil. Even Phil Tenacious Oil contains the same class of oil and even a similar molecular weight range. The oil is what makes WD40 such a crappy solvent, it’s the residue that it leaves behind. It’s now better but also no worse than any mineral oil that might be used for this application.

Just to be clear (I’ve said this before), I’m no lover of WD40 but I’m not a hater of WD40 either. It works for some applications. For a consumable like a freewheel that is relatively cheap, it’s not going to do any harm. If the freewheel is gummed up, it’s on well on its way towards the recycle bin anyway. Frankly, I’ve spent more time on this thread than I’d ever spend on a Suntour freewheel.

If you're going to argue that ATF shouldn't be used as a lubricant because it was designed to be an application-specific hydraulic fluid, you don't get to argue that WD-40 should be used as a lubricant or a solvent, since it wasn't designed to be either. WD-40 was designed to be a water dispersant (hence the "WD") and rust preventative, for use as a surface preservation treatment for ICBMs. (Airman Schmuckatelli had to apply it to the outside of the missile with a mop.)

Of course, it turns out that both of these things can be used outside the applications for which they were designed, because, as you said, light oils are fairly interchangeable, especially in extremely low-stress applications. Like, for example, the <0.5 HP power, <500 rpm environment of a bicycle drivetrain. All anyone is saying about the product that you seem to have an oddly intense need to advocate and defend is that it's not ideal for the applications under discussion, and that there are better choices.

Which there are, because it isn't.

--Shannon

If you're going to argue that ATF shouldn't be used as a lubricant because it was designed to be an application-specific hydraulic fluid, you don't get to argue that WD-40 should be used as a lubricant or a solvent, since it wasn't designed to be either. WD-40 was designed to be a water dispersant (hence the "WD") and rust preventative, for use as a surface preservation treatment for ICBMs. (Airman Schmuckatelli had to apply it to the outside of the missile with a mop.)

Of course, it turns out that both of these things can be used outside the applications for which they were designed, because, as you said, light oils are fairly interchangeable, especially in extremely low-stress applications. Like, for example, the <0.5 HP power, <500 rpm environment of a bicycle drivetrain. All anyone is saying about Water Dispersant #40 is that it's not ideal for the applications under discussion, and that there are better choices.

Which there are, because it isn't.

--Shannon

I’ve never used Phil’s tenacious.

My experience with WD is it gums up over time.

I use almost anything at work because I’m only using it to lube threads and I don’t care about those threads 2 years from now. But triflow has some Teflon in it.

I advocate synthetic ATF only because in my experience synthetic ATF takes a long long time to gum up. Mobil 1 or a synthetic gear oil would probably also work for a long time.

Cap and ball is fun. I want to take an elk with a .50 muzzleloader one day.

.
...because I, too, have experienced the alarming shortage of 5 an 6 cog freewheels, in the 14-26 and 13-24 ranges that I use on a lot of things I own, I have been forced (by necessity), to start re-cogging some, using scrapped freewheels from the co-op as my source for cogs. The Suntour freewheels are really good for this purpose, because there are a lot of them in the used parts stream that still have cogs that are not worn out.

But the only way I can get them dismantled most times is by using a mix of acetone and ATF as my penetrating oil. Even then, I often need to heat them with a MAPP gas torch. I'm certain this is not what ATF was designed for, but it sure works well.

As for writing off Suntour freewheels as beneath your dignity, I can only refer you to the prices commanded by the 14-26 five and six cog ones on ebay currently. I do Shimano 6 cogs too, with their better shifting cogs, but the earliest ones in five speeds have an annoyingly small center hole, which will almost, but not quite, fit over a campy hub lock nut. Which is a PIA.

You found a way that works, so take this with a grain of salt.

I found a mix of charcoal lighter fluid and triflow worked for a good penetrating oil.

Context was 2” or 3” nuts on bolts, nut side up. I think a big impact 1 1/2” anvil wasn’t breaking them loose. Torched one off but realized it was going to be extremely slow going to do that ~50 times or whatever. So I squirted triflow and lighter fluid on every thread and went home. The next morning every single nut broke free pretty much immediately.