Originally Posted by Barchettaman

I´ve disassembled, cleaned with solvent, liberally regreased and reassembled the headset.

There was no sign of wear to the races or (caged) bearings.

The bloody thing hardly turns at all now! When I tighten it enough to eliminate play in the fork, there is loads of resistance at the handlebars.

Could I have overdone the grease?

The ONLY thing I could have done wrong as far as the reassembly order goes is to put the caged bearings in upside down on the races, and I am 90% sure they have gone in as they came out.