Lightweight cam shafts

Previously wrote:

As some might know, I am in the process of restoring a Norton Electra. The camshafts are showing signs of damage on the lobes. I do have the manual and (Provisional) parts book photocopy from Bruce Main Smith for the bike. I am wondering what the differences are between the cams for Jubilee, Navigator and Electra are. I would obviously like to find new replacement cams, but I suspect these are about as easy to find as rocking horse turds or hens teeth...

The cam followers are worn, but I'm hoping that if I make a suitable fixture I will be able to re-surface these with a horizontal grinder and a hone on fine wet and dry paper taped to a surface plate, just like I did with the ones for my 650.

I had the same information as you, and the same problems. I've got a bit more information now.

All lightweight camshafts are made from the same forging. The forging number (22235 I believe) can be seenon all lightweight camshafts and does not appear in parts lists.

All lightweight inlet camshafts look similar. Jubilee inlet camshafts carry the identifier I7, stamped into the non-gear end or on the shaftbetween the cams. Navigator and Electra camshafts carry the identifier I5N. Navigator and Electra use the same camshafts.

Jubilee exhaust camshafts carry the identifier E7, stamped into the non-gear end of between the cams. Navigator and Electra camshafts carry the identifier E5N. Navigator and Electra again use the same camshafts.

You wonder what the differences are?

The peak of Jubilee and Nav/Electra cams is at exactly the same point of the four stroke cycle. The Nav/Electra cam form is practically identical to the Jubilee cam form with the following exception.

The base circle diameter of the Jubilee cam form is 10 thou greater than the Nav/Electra.

The camshaft lift is 1.225/9ins on I7/E7

The camshaft lift is 1.235/9ins on I5N/E5N

The smaller base circle diameter on the Nav/Electra cam form give a slightly earlier opening and slightly later closing. Norton were limited by their decision to use the same forging for all lightweight camshafts.

Armed with this information and a micrometer you should be able to identify lightweight camshafts at any autojumble.

The NOC Spares Scheme has some Nav/Electra NOS inlet camshafts.

Also plenty of cam followers which wear badly on their shafts. Measure top, middle, bottom diameterswhen checking for wear. They wear into a barrel shape and then can't keep the follower flat against the cam.

Good Luck

Peter Holland