Bicycle Mechanics - need a new freewheel or just derailleur adjustment?

I just inherited my father's mid 70's merckx with a full campy group. I usually ride a fix, so I'm not too used to shifting or derailleurs. When I'm pushing the cranks hard, the chain skips on the cog. It doesn't shift or anything, just slips a few teeth. As far as I know, it is the origional freewheel and my father rode quite a lot, so I was thinking that this was an indication that I sould be looking for a new freewheel, but I wasn't sure. It had not been ridden in about 10 years so I also thought it may just need some adjusting.

If a new freewheel is in order, where should I look for one? I'd like to get one that is in keeping with the quality of the rest of the components and, if possible, close gear spacing for triathlons.

thanks
tim

It could be one or more freewheel cogs, the chain, and/or the jockey wheels that are worn. Is it happening primarily on one cog on the freewheel? BTW, if indeed it's the freewheel, then you can bet it's time for a new chain as well.

Another possibility, and esp. if it's happening on the smaller cogs, is a stiff chain or stiff link on the chain. That's usually easy to spot by turning the cranks backwards (you can do that on this bike, y'know ;) ), and looking at how smoothly it passes around the cog and thru the jockey wheels.

Try to look down at the rear wheel when it skips. You can usually tell if the der is out of adjustment; the chain will appear to be being tugged either left or right by the derailleur.

thanks.
I played around with it for a bit and found that it only skips on one cog, the 4th highest, so probably 15 or 16 teeth. it seems to be the most often used cog. can I replace just one cog on a freewheel or must I get a whole new one? I guess I'd prefer replacing the freewheel and chain now just so they won't cause prolems in the future.
so that brings me back to wondering where I can get a good freewheel...

tim

Yeah, freewheels can be disassembled in order to replace individual cogs. But you're probably delaying the inevitable; the other cogs may be less worn, but not by much. And a whole new freewheel probably won't cost much, and will give you all new internal mechanics (pawls, ratchets, etc) to boot. Check eBay, sales at the LBS, etc. You'll need to identify your existing freewheel and try to find as close a match as possible. It'll have to be the same number of cogs, and the same hub threading, at least. And if you plan to do it yourself, you'll need a freewheel puller for the old freewheel (which, if you get the right new one, will also fit it).

As for the chain, it's probably due for a replacement as well, as they wear at least as fast as cogs/chainrings. A quick test: put a tape measure on one of the pins, and count out twelve full links ("outer" PLUS "inner" plates). It should be just about 12" from the starting pin. If it's 1/16" or more beyond 12", the chain is worn and should be replaced.