How new is it? Will and myself have found that new profiles have about a month of bedding in, after which all the loose bits of pawls/springs/teeth etc end up inside the mechanism causing it the skip like a maniac. It sounds like you've had a worse experiance than I did, but not unlikely that this is the same case Heres a quick check for it Take the wheel off and the axle fun bolts for drive side. The driver should just pull straight out but may require some tools or a lot of force. If it falls out though, don't worry With the driver (the bit with the cog on and about 4 bearing races inside) out, you should be able to see some small pieces of metal on the other part of the hub (usually, it gets stuck on the axle bearing rubber seal but check everywhere else too) If you can't see any bits, read a bit lower down, but if you can, get a small brush like a toothbrush and gently clean all the bits onto a rag for binning. Reassemble the hub and it should work fine If you can't see any bits Leave the hub and go back to the driver. You should see the 4 pawls sticking out in a nice pattern. First check the springiness of the pawls, do they even go in? or is there some dirt preventing it? Clean if so If they go in and don't return (or indeed were never sticking out in the first place, see if you can see what is happening with the spring steel. Does it need a slight bending out to keep the pawls spring loaded? Are some of the springs missing. Whichever the case, you may need to order some new springs, which some kind TF member will locate a cheap place for buying them separately, im sure Other than that I can't think of anything, sorry Hope this helps though