The tight mainshaft end play in the old instruction books is really only for when the old angular contact Timken bearing was used on the clutch side! That bearing required a very tight endplay in order to work properly. A different type contact bearing mounted from the outside, was also used on the older gearboxes and also required that tight setting.
With a modern deep groove ball bearing at the clutch side, that tight endplay is not critical. Don't ever use a angle contact bearing whatever!, but use a modern common ball bearing (6207 2RS), then the bearings acts as end stops not relying on bearing preload settings. The mainshaft is free flowing.
With a modern single row ball bearing on the clutch side, end play must be present and loose is better than too tight. An audible click-klick is good and Ok. It is up to the mechanic but I set it up to max 0.01" or 0,25mm.
Rather shim thicker at the clutch side if needed, because the shaft protrusion past the sprocket gear should be as large as possible. That is important because the (hardened!!) washer on the outside for the kicker ratchet spring must not touch the large nut or the sprocket. If the washer touch there, return of the kicker pedal is hampered when the engine starts, with an annoying ratchet as a result.
Sorry for the out-of-focus picture but I am pointing on the ledge on the mainshaft that must protrude in order to avoid the spring washer to make contact with the nut or sprocket.
