A review of correspondence from NOC-L
In order to avoid premature wear and oil leaks, it is necessary to align correctly both the primary chaincase sprockets and the chaincase itself
Align the chain centrally on the sprocket teeth
Aligning the front and rear sprockets in the primary is very desirable to avoid premature wear and reduce vibration (even if your Isolastics prevent you from feeling it!) When I did my bike, I simply watched where the chain sat on the clutch sprocket after rotating the engine. As it sat with the teeth pressing against the outermost plates of the chain, I simply reduced the shims behind the clutch and repeated the process until the teeth sat dead centre of the chain after rotation.
Martin Edridge (firstname.lastname@example.org) on NOC-L 12th. May 1999
Align both the sprockets and the chaincase
It is a good idea to align these sprockets up as accurately as you can, as it puts the run of the chain in a direct straight line between the two sprockets. This stops the chain side plates from rubbing on the sides of the sprocket teeth resulting in extra wear on all components. Also you don't need the loss of horse power that goes with grinding away your primary drive.
Take a steel rule or straight edge and hold it against the side of the engine sprocket and see where this line comes in relation to the teeth on the clutch basket. It's best to do this without the chain on the sprockets so you can rotate everything and try and average it out in different positions. Even with the bit of wobble that seems to accumulate through the gearbox mainshaft and clutch basket you will get it fairly well in line. Simply add or remove shims from behind the clutch. There is a thicker spacer (about 4mm thick from memory) with a small recess in the bore to go over the snap ring on the mainshaft. This needs to stay in place and the shims are added or subtracted outboard of this.
Regarding the inner primary chaincase, this is fixed to the engine with three bolts, with a gasket between the primary and the engine case. There is also a through bolt that is fixed to the steel engine/gearbox cradle. This bolt passes through the inner and outer primary covers and has a domed nut on the end of it that holds the primary outer cover on. Before you put the outer cover on, get a mirror and look down behind the inner cover (between the engine cradle and inner cover) to where the through bolt comes up against the inner primary. The inner primary will sit against a shoulder on this bolt. You should shim this shoulder so the inner cover, as it's bolted to the engine, just touches the through bolt shoulder, so when you put the outer cover on and tighten the domed nut, it will not pull the primary chaincases across sideways and pull it out of shape. If there are too many shims/washers on this bolt before you assemble the chaincase the inner will sit proud or at an angle to the engine and won't sit flush against the engine where the gasket and three bolts hold it, and will consequently leak.
Bob Davis (email@example.com) on NOC-L 12th. May 1999
Align the sprockets with the chain removed
Assemble the engine sprocket and clutch without the chain or inner case. No full torque on the nuts is needed, just have them nicely snugged. Now a good solid straight edge can be placed against the teeth of each sprocket; any misalignment will be obvious. Remove the clutch to adjust shims as needed, reassemble to recheck. them. Then you must have it all apart again to install the inner case.
Ben English (firstname.lastname@example.org) on NOC-L 13th. May 1999
Align the sprockets with the chain removed
I don't know anyone who does their primary chain alignment the way that the manual recommends doing it. It's hard to believe that Norton recommended aligning it on the inner primary case, although I know they did.
The way that I do it is put assemble the clutch basket, engine sprocket, and alternator rotor without the primary chain. Then check the alignment of the gearbox sprocket and the clutch basket; it is easier to do this with the inner primary cover removed as well. Add or remove shims behind the clutch basket to align the two. Since you cannot tighten the nut holding the alternator rotor and engine sprocket fully with the primary chain missing, the engine sprocket won't be as firmly on the taper of the crankshaft as it would with the chain in place. For this reason, if I cannot shim the two to perfect alignment, I prefer to err on the side of having the engine sprocket further out than the clutch basket.
Eric Goforth (email@example.com) on NOC-L 13th. May 1999