thanks guys for the info, feel a lot more confident taking this on now, seems fairly straight forwards...but before i do...quick question, which 35's does this affect?? upto what serial number/year or is it just all 35' with a leather seal, mine is 1980's one of the later ones to be made with leather piston seal as i understand, had the problem been sorted by the 80's?? anyone know? or is it best to do the fix as a precaution anyway whilst fitting new spring an top hat etc, also the conversion parts for changing to a synthetic seal...worth doing? my leather seal looks like new after 24 hours in neats oil.... thanks again fellas