What size?

[nobby]

What size is the top yoke nut on a 600?
mines a 93.
I wanted to just nip up the head bearings and go for an early MOT but dont have anything that size.

If any know then I will get a socket the right size.

[CD]

Tape measure?

Joking apart, it's worth buying a suitable tube spanner, though sometimes a big adjustable will do the job.

Grannies n eggs...
The top dome nut simply holds the top yoke in place. The bearings are adjusted with the slotted nuts under the top yoke. That dome nut should not be silly tight.

If the steering bearings are duff - tightening them will make the steering knotchy.