ok, a while a go i bought a kmc kool chain and fitted it to my zoo pitbull.it was jumping like mad every few pedal strokes so i spaced out my mech and tried the sprocket in different plaaces on cassette to check the chain alignment was alright. but still didnt fix the problem!! so i bought a surly rear splined sprocket and it was fine for a while then it starting skipping again!! so i bought a khe collapse chain and a new surly rear sprocket! still no better!! i have set my mech up perfectly in line etc and it is single speed on a chris king hub, my mech is spaced out, chain alignment is good, i dont have a stiff link!!!, chain is nice and tight and i am really baffled about it!! any ideas people?? thank you