HI Andy,
""The oil seal dist piece measures about 10 mm, the sleeve approx 51 mm overall and the lip about 5 mm thick. How does that compare? ""
Distance piece measurement ok.
Attached are a couple of photos showing two cush drive sleeves and a good and two butchered crank nuts for comparison
It looks as though finally the discrepancy has been found
(At least one of????)
The sleeves in the photo have the shoulder just over 8mm thick, overall length about 50.5mm
This would have allowed the sprocket on your bike to be 3mm in too far,
the packing spacers were added to correct this BUT have moved the sleeve and nut outwards by the same amount,
probably why the nut is touching the outer casing??
When the assembly is together, a point to note is that without the spring in place it should NOT be possible for the sprocket to ride over the top of the shock absorber cams.
I think you need the proper cush drive sleeve as a start off point.
""The only other dimension I can think of is from the front face of the crankcase, face where the 5 tapped holes are, to the machined face of the gearbox boss is about 25 mm, see photo. That should indicate if the G/B is not correctly located?""
I dont have a bike in that state to take a measurement at this time, perhaps some one else has?
""Does/would the single cyl adapter directly fit the center I have or would that too have to be replaced?""
Its a direct replacement its just thet it sits farther onto the mainshaft (probably not needed now ??)
""The SRM looks to be a better idea by have concern that the allen screw, with my existing problem, will end up chewing up the inside of case as the existing nut does?""
The allen screws are not used when the bike is assembled for running, they provide a mounting for SRM's timing disc
""The SRM clutch basket also looks to be a possible solution. Would have to check it's depth. Would it also have the bottom plain plate sitting on the center lip?
""
Normally Yes,
or
SRM's shaft adaptor has provision for a thrust washer,
http://www.srmclassicbikes.com/catalogue/index.php?target=products&product_id=158if this is fitted the lip on the inner drum can be machined off
or enlarge the centre hole in one friction plate so as it will fit over the lip, so as the first friction plate will sit in the bottom of the Basket,
""Much appreciate your time and help, the same goes to everybody else who has replied and contributed, thanks.""
Many Thanks
Hopefully tomorrow I will get at the gearbox questions,
can you temporarily assemble the mianshaft and inner case + the sprocket and nut and measure as before
Regards
John