To fit the rocker arm bearing assembly, it is necessary to press out the old outer bearing race and side washers, and press in the new outer bearing.
To do this really requires some form of press (although I am sure the correct spacers and a good vice could also do the job!). Then once fitted, the outer bearing should really be honed, as it is inclined to close up fractionally as part of the pressing in process.
With this in mind I offer a service to take your old rocker arm (which you should post to me fully insured), and I will fit and hone the complete bearing assembly. The rocker arm will be sent back to you with the bearing assembled and honed, side washers fitted and the assembly lubricated with castor oil. (Please note though, the cost quoted is for a standard rocker arm, fitted with a standard Norton bearing. If the arm has any other issues that requires resolution, these may be additional). Price is per Rocker Arm. Postage back to you will be additional to this, and the rocker arm will be sent fully insured.
Note: this honing service is carried out on a professional honing machine - a Delapena Speedhone, probably very similar to the one used by Norton's themselves!