Hi, should the two front sleeve nuts and the rear nut on a 750 cylinder head have washers?
The strict answer to this is no. Decently made Dominator sleeve nuts with a hexagon spanner end and a rounded end for the barrel fit flush against the respective faces front and rear. Having said this, on all my Norton Twins I put a quality thick washer under the rear nut. This saves a good number of part spanner turns when replacing the nut in that very awkward position.
Now the contradictory bit............The early Commando front sleeve nuts are full-length hexagon shaped items and do have washers under them. I always swapped mine for the Dominator versions which didn't need three hands to fit them in place. Strangely, the later Commando engines managed to lose the washers.
I cut a cranked ring spanner in two so that it only needed about 30 part turns instead of 60. I still find it useful for awkwardly situated nuts despite no longer having a Commando. Final tightening was easy with a short bit of tube slipped over the shaft.
The other useful tool was an Allen key with the short leg shortened to about 1/4" and the long arm bent to avoid catching things.
During the years, I've have came across a couple of badly engineered machinery, where an hex screw would be easily to fit but a cretin had designed it with an Allen screw not readily accessible. One way is to use a 1/4" ring spanner and a bit. Some electrical tape to hold the bit in the spanner.
Sorry for messing up a washer thread.