Jubilee Camshafts

Jonathan,

I have samples of both early and later camshafts.

The cam profiles appear to be the same.

The detail for seal and auto advance fixing seem the same.

The bearing surfaces seem the same.

All the above on visual, not metric inspection.

It is obvious that the later Jubilee camshafts have a hole in the drive side end to take a spring and plunger to press against a steel disc that is present behind the drive side camshaft bushes.

Why the change?

It wasn't cheaper so I presume there was a problem of noise, or stability of the points cam. The early camshafts are free to rattle left and right within the axial play provided by tolerance build-up.

This change came about very early in the lightweight history.

Probably better to get the correct style for your bike because the very early Jubilee crankcase (which I haven't seen) probably does not have the steel discs behind the drive side camshaft bushes. It didn't need it.

Perhaps someone with more knowledge can shed some light.

Peter

Exactly as Peter says above.

The first jubilees did not have spring loaded plungers in the end of the cam.

There was no easy way to minimise end float, and so the cams rattled left & right with whatever torerance they had.

This was not satisfactory, so a steel disc was added to the end of the tunnel on the Drive side of the engine - & plungers were added to the end of the cam to soak up the end float.

There is no other difference in the cams.

Stampings on the end (by the plunger are: I7 = Inlet Jubilee, E7 = Exhaust Jubilee; I5N = Inlet Nav & Electra; E5N = Exhaust Nav & Electra