Such question reminds me of one of the Sheldon Brown's April Fools Day articles on chain cleaning. In short:
- disassemble each link by driving the pins out
- clean each part individually and thoroughly
- lubricate the moving parts
- reassemble (reverse of disassembly)
With his sets including the chain break tool, all chemicals and some replacement parts, ranging in price from $69,95 to $249,95 you're good to go.
But let's get serious - as many say, it can be done. It only depends on economy, i.e. your imaginary hourly rate. Be prepared to spend couple (2-3) hours on cleaning the chain and making it work more or less properly. And all this in hope that the chain has proper dimensions (is not overstretched).
To give you some indication on what can be done have a look at the small part of the chain that I cleaned last weekend:
It's a piece of chain that started rusting in the early '70s. After soaking it in phosphoric acid for about a quarter and then cleaning, lightly sanding (120 grit if I'm not mistaken) and polishing it with some paste for a following quarter it's the result I got. And it's only 5 out of more than a hundred links.
Was it worth? Financially not. And I wouldn't put this chain on a bike (reliability and the ease of maintenance).
I did it because a) it's a respected vintage brand from where I come from, this chain has some interesting history and I was making a key-chain (pun intended) for someone to keep this as memorabilia.
- phosphoric acid is a hazardous substance with corrosive characteristics. At moderate concentrations phosphoric acid solutions are irritating to the skin. Contact with concentrated solutions can cause severe skin burns and permanent eye damage.