Have you removed the grub screw?
The steering lock is normally retained by a grub screw (21-0578), and is then sealed over with a 'sealing washer' (97-2266) to prevent tampering.
Look for a small circular indentation at the front of the yoke immediately ahead of the lock, also look at the fork diagram (pdf p.48) in the link below.
Grub screw and sealing washer see pdf pages 48 & 49 (1978 parts book, but the lock assembly is the same for a '76 model)
If you drill out the sealing washer and remove the grub screw you should then be able to remove the lock by knocking it upwards out of the yoke?
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