Just typed out LOADS then, and it didn't come up Anyhoo... I'm guessing you have an ACS. Have you ever serviced it? Basicaly, take it off (or just crank arm) and take off the lockring. Lovely, bearings and everything to play with. Take it all out, but keep it all clean and safe. Clean out the body of the freewheel with kitchen roll/cloth etc. And clean out the bearings etc. Coat it all in WD40/GT85 etc too. Then put it all back together. First put it all in the body. Then start with the springs, then the pawls (think thats what they're called) Then the bottom side of the bearings. Once they're all in, do the same on the other side. And then put on the lockring. For the lockring, it's best to either Locktite it on really tight, or weld it. Personaly, I'd weld it. I'd trust it a lot more staying together. Now you have it all together, spray loads of WD40 etc on it, and it shouldn't skip. If you've buggered it up - Profile and an 18T cog for rear cassette, ENO (72ep) and your current 12T cog, or wait a while and get the new Tensile freewheel (48?ep)