Hello folks, first of all, I am new here. BUt I have a chain question.

Before the question, here is a little back ground info. I have a single speed bike, the rear has a ratchet style drive (forgive my lack of technical names for everything). I recently bought a new chain ring for the crank. The chain ring came off of a multi-speed bike, though. I managed to do some hack sawin, grinding, and filing to get it to go on my crank (it is larger than the original ring). I bought the ring (which was still attached to a crank) from a man at a local bike shop. After I got the chain ring on, bearings greased and reinstalled, I called to see if he could sell me some chain. He couldnt' at the time, so I plan to go tomorrow, but he said if I wanted I could go to walmart and buys some. He warned me to NOT get multispeed chain, as it would not work for my application. BUt as far as I Could tell, the only difference in the chain on this paticular bike, and all the multi-speed bikes in my garage, is the width of the chain. the diameter of the rollers is the same, the center to center distance from each roller is the same (I beleive this is called pitch, someone please correect me if I am wrong).

So finally, my question. Why would mutlispeed chain not work?

The main reason I'm asking is that I plan to attempt to convert this to a two speed some time, so I figured knowing more about the types of chains would be some handy knowledge.

Thanks in advance,

Nic