If I change from a lay down box to an AMC box do I need to change the rear engine plates?
No. I have changed from mid 1950's single downtube frames from laydown to AMC style 'boxes without any change in the mounting plates. Be advised there are at least two different lengths of input shafts in these gear boxes (maybe more?) and so you have to watch for chain alignment between the engine sprocket and the clutch sprocket. In addition you need to watch for clearance between the output sprocket and the back of the clutch (attention to the rear chaincase if you are fitting one). There are three different engine sprocket offsets also on singles. I would refer you to RGM Nortons for their catalogue descriptions. I have also had problems with swinging arm frames not allowing the rear chain to clear the structural tie across plate with output sprockets of less than 19 teeth. I am going to change mine to 21 teeth to accommodate this and reduce the size of the engine sprocket to compensate. Best o' luck!
Thanks for your thoughts Geoffrey, however, I am going to refurbish & refit the original.
Thanks. There were at least two input shaft lengths for the laydown 'box to accommodate the different frames that Norton fitted with these units, so it is just not with the AMC 'box. In searching the parts books I discovered that on the swing arm frames, the minimum output sprocket listed is 20 teeth. As I noted, I would feel more confident with 21 teeth. Cheers!
Having decided to refurbish the laydown gearbox I purchased the five outer tang clutch friction plates as shown in the diagram, to replace the worn originals from the NOC shop. However, on assembly the stack of friction plates and steel plates cannot be secured with the circlip.
If I remove one of the friction plates there is a gap between the final steel plate and securing circlip.
Does anyone have the solution to this problem please?
found the circlip necessary and like you have had clutches which didn't have room for it. The clutch doesn't lift enough to let the plates out in my experience.....
Thanks for your thoughts Ian.
Did you replace the cork inserts?
I have read reports where the cork inserts need to be sanded to make the correct stack height.
Is that correct? Knowledgeable folk will reply I am sure.
A Norton clutch never used cork inserts.They were fitted with Ferodo inserts. I don't know if it was the same material as brake linings... They were made so that owners could replace them when they got worn. The inserts for the clutch chain ring are thicker, and much harder to obtain than the regular friction plate inserts.
The reason the new plates are thicker is that the plates are solid with the friction pieces glued on either side. These need to be a reasonable thickness to be durable and this makes the plate that much thicker compared to the original windowed type where the inserts alone govern the thickness. The clutch will work better with only 4 new plates, and as Ian says, the circlip is not needed. The only thing you need to check is that there is enough adjustment on the worm-screw or if you need to shorten the long push-rod.
Thanks to all for your replies and thoughts.
I have not replaced the chain wheel inserts as they appear to be ok. (time will tell)