[jambo]

Sosha's quite right, as are the others who've suggested / offered assistance. It's very easy to overtighten headraces when adjusting them, this leads to the bike weaving slightly as there's a little friction stopping the bars straightening up perfectly. It will also dramaticly reduce the life the bearings have left.

Loosen the bottom yoke clamps off, then the top steering stem nut, then tighten the ridged nut underneath the top yoke. Tighten it untill there's the smallest amount of resistance. Ideally you want there to be a little play in the head races until the steering stem nut is torqed back up. Don't forget to have a bounce on the front end, then do up the bottom yoke bolts.

Jambo