I fitted a 5/8 x3/8 chain final drive chain to my 1952 Model 7 plunger, from the spec in a Main-Smith manual. Got the bike running, registered and then found a couple of oil leaks. So took it apart this winter and noticed the chain had rubbed the face of the gearbox and also the inside face of the chaincase.
Did I fit the correct size chain or should it have been a 1/4 in chain?
The teeth are 5.5 mm at the tip of the teeth and 6 mm at the base both gearbox and rear sprockets. There seems to be a fair bit of space difference between the teeth width and the roller width.
You are quite correct......even the Norton Maintenance manuals have the wrong chain size for the model 7. Possibly it was designed for a 3/8" chain but this was sensibly changed at the last moment to give more clearance.
Attachment is from Norton offering for all Model 7s from 1949 to 1955. If you think this is poor the 650 parts book is even worse.
This spec page looks as though it’s been copied exactly into the Main-Smith manual. It’s been a frustrating first venture into classic bikes but I can’t deny I’ve learnt a huge amount, not least from these forums. I think the most telling comment I’ve come across was from Mick Hemings in the engine rebuild video, when he says something along the lines that even Norton didn’t know what was being used to build their bikes...
... I rely on Edgar Franks, whose book correctly states the size as 5/8" x 1/4". This size was used for all Norton models till the Commando.
...and post 66 650SS/Atlas 'Dominator' models.
.. I didn't know that. Presumably they had to modify the inner primary chaincase to get clearance?
Whst I do know is that when I fitted a 'heavy duty' 530 chain, I had to put the spring link on the inside run to stop it eating the case. Now have a riveted link HD chain on so no issues.
Probably find that AMC just bent the case a bit to make it fit!
... fit the spring link on the inside of my ES2! (5/8" x 1/4"). No way anything thicker would have fitted.