If you look on sheldon browns website it gives details of how to have the correct chain length, but I suspect that the sprockets are worn in your case hence the skipping. Link here as to what you should be looking at.
http://www.sheldonbrown.com/chains.html
@lynx started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
If you look on sheldon browns website it gives details of how to have the correct chain length, but I suspect that the sprockets are worn in your case hence the skipping. Link here as to what you should be looking at.
http://www.sheldonbrown.com/chains.html