rvich said:
I would have thought that they would have stayed with the MB41 deignation for as long as they kept the rear drum. But this just goes to show you what I know!
Can you say what diameter are the spokes are, and are they straight wire or "butted" (two diameters)?
Also what diameter are the nipple holes in your MC286 rim?
Could someone also please supply the MB41 rim nipple hole size for comparison?
I cross-checked the rear wheel part numbers in the 850 Mk2/2A supplement with earlier rear wheel assemblies and there are a number of changes in the 2/2A supplement which include rim, spokes, nipples, hub, brake drum, axle, etc.
Cross-checking that information with the workshop manual specifications and by doing a bit of detective work, it appears the rear wheel spokes may have been changed from the previous butted 8/10 SWG to 9 SWG (or 8/9 SWG?) for the 850 Mk2 & 2A models.
The increase in spoke gauge may have required the rim change to one with larger holes for the 9 SWG (063207) instead of 10 SWG nipple size, however that is a guess-as an increase in spoke diameter does not always require a larger nipple diameter and the part number change could have been for a completely different reason (the rear rim is listed as 065730 in the 2/2A supplement)?
Unfortunately, using the Andover Norton part search, the majority of those different 850 2/2A part numbers come up as: "Part not found" and the AN rear wheel parts listed for 1974 appear to be the same as the earlier year models except for the spokes which seem to be listed under different part numbers to both rear wheel types.