Merry Tiller Cadet / Wizard drive belt probs.

Hi, any of you MT experts still around?
My Cadet / Wizard 'drives' ie turns the tines even though the clutch is not engaged, fitted a new 'Loncin' engine about 18 months ago and today fitted a new pulley and belt (because the pulley had a big lump out of it and the belt was u/s because of this problem). Any help and/or advice gratefully accepted, thanks, Cliff.

Thanks R Tallentire, It turns out I was (possibly) barking up the wrong tree, some months ago I purchased a spring from you because I believed one was missing from the bottom of the clutch cable to the clutch skate lever, however I didn't fit it because my Father (who's machine it is/was) convinced me that he nor anyone else had removed a spring, however yesterday I realised the belt was slipping, so fitted the spring which tensioned the clutch pulley which tensioned the belt and appeared to make it all work again! Now I just need a chain case bolt which has suddenly disappeared () to stop it leaking oil! Thank you for your reply and pulley and belt! Cliff.