Primary chaincase assembly

As I continue to disassemble and inspect a 1970 parts bike I am reminded of things that make riding a reliable Norton easier.

I took apart the primary chaincase and noticed a vertical crack on the inner case. Then I saw that the was not a washer or shim between the chaincase center stud and the inner case. When the chaincase attachment nut is tightened up the cases will flex inward and stress the 3 chaincase bolts area of the casting.
I also saw that the back of the inner case was rubbing the swingarm left hand end cap. All this damage could have been avoided if the inner chaincase was properly assembled with the correct shimming of the center stud.

Oh, and correct shimming of the clutch sprocket to run true to the engine sprocket is even more important.

Why is that picture upside down?

Dave
69S

I just put my primary inner on and found that i only needed a shim for proper setup.
Is the washer a must have?

xbskt said:

I just put my primary inner on and found that i only needed a shim for proper setup.
Is the washer a must have?

Click to expand...

I suggest that if you have the engine sprocket and clutch hub off then slightly loosen the 3 chaincase bolts and visually check if there is a gap between the inner chaincase and the center stud, also check if the inner case is clear of the left swingarm endcap.
If the primary chain and sprockets are still in place then just remove the outer primary cover and visually check if there is a gap at the center stud or not.

The point is that you don't want to put a flexing stress on the primary cases when you tighten the nut.