If the original superblends are still fitted they will be the very special Ransome and Marles roller race bearings marked 6MRJA30. These had narrower rollers than the 8MRJA30 non 'superblend' bearing used previously for the D.S. bearing.Also it is interesting to realise that the 6MRJA30 bearings used as part of the cure for the 'oops the mains are rumbling and I have only done 4000 miles' problem have a lower static and dynamic load capacity than the roller bearings used previously. If you ever take one out remove a roller and get it very accurately measured and compare it with a roller from a bearing they call 'superblends' these days..There is a big difference and the olde 6MRJA30 bearings would allow a lot more crankshaft flex.......
Not that anyone will be interested.ALL approx.
8MRJA30. 11 rollers. parallel portion of roller 10mm wide with no barrel shape to them. Total width and Dia of a roller 11.12mm Load capacities...Dynamic 41,900N. Static 35,200N.
6MRJA30. 13 rollers. 'parallel' portion of roller 6mm with a dia of 9.53mm reducing to 9.46mm at the edges. Total width of a roller 9.53mm. Load capacities...Dynamic 35,800N Static 31,000N.
Shape of a roller in the FAG and RHP 'superblend 'bearings I checked decades ago...
Total width 12mm. O.D 11mm for 8mm width reducing to 10.96 mm at the edges.
I heard the ONLY reason Norton changed to FAG bearings was that they were just down the road.2 They were cheaper than the special 6MRJA30 bearings BUT I could of been told wrong. Of course the load capacities for a FFAG NJ306E bearing are a LOT higher at Dynamic 51,000N Static 48,000N and for a RHP NUP306ETN Dynamic 57,000N. Static 53,000N.
However bearing material technology has changed a bit since the days I was given thes load ratings by the manufacturers
INTERESTINGLY...the drawings for the 6MRJA30 bearings a gent dragged out of the cellars for me many years ago at the old Ramsome Newark factory state the bearing was a CN fit/ internal clearance. Now I bought a few in Brum after Nortons had gone bust and all measured a low C3 fit.
NO SPELL OR GRAMMER CHECKS.