Originally Posted by
oldukbkr
Go back to where you had this serviced and ask them to check the freewheel for wear. Most likely the skipping is because the freewheel cog is worn out and you need a new freewheel.
Strictly speaking what he needs is a new 14t cog, not the whole freewheel. For many brands, cogs aren't EASILY avalable, so it amounts to the same thing — replace the whole freewheel. Almost anything can be found if you're patient and know where to look, so I wouldn't rule out finding a new top-gear cog. I probably have some, I have many brands to cannibalize for parts, but I'm not a dealer, my junk pile is for working on my own bikes. But try
Freewheel Spa maybe? That's BF's own
pastorbobnlnh , highly regarded, the best!