clutch casing

[ben.measures]

i recently have removed my clutch to find score marks in the outer/inner casing.
Am i missing a washer or a spacer?

[pete.collings]

Not necessarly, there can be slight variations in clearance dependent on the exact positioning of the gearbox and primary chaincase inner in the frame, also if there is a little wear on the chainwheel needle rollers/centre this can allow the clutch drum to move a bit and catch the outer chaincase.
I have encountered this before, the solution is to put a new/used flat six holed clutch drum lockwasher behind the clutch drum to push it outward a bit. If it takes more than one lockwasher, then you need to look at other alignments (as above) a bit closer .

[pete.collings]

I should have added that the other cause of the clutch drum touching the outer primary chaincase is using an earlier (52-55) GB gearbox in a 56-59 bike. The mainshaft of the earlier box is around 1/8" shorter than the later ones, and as the parts are interchangeable it is possible to fit the earlier mainshaft in a later gearbox. The difference in length is in the section that the sleeve gear runs on, this was to allow for the Fully Enclosed Rear Chaincase fitted to 56-59 models.
This difference in length usually results in the clutch drum locking against the primary chaincase, although attemps to space it out (as in the above posting) might allow it to run, but with minimal clutch/chaincase clearance.
I think the mainshaft dimensions are given in the Knowledgebase.