mystery service bulletin? mixing gears or made pairs

https://www.accessnorton.com/NortonCommando/gearbox-identification.18335/page-2#post-368115

Nortons put out a service advisory/bulletin when the 2nd version of AMC gearbox appeared,
warning also not to mix the different types of gears and always to install them as made pairs.
Anyone got that handy, to quote from exactly. ?

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all i've come across so far
http://preservationcycle.com/index....-norton-commando-gearbox&catid=86&Itemid=1739

In 1968, at number 128646, the high gear pair was modified for strength and durability, and these gears must be a matched set. The tooth profile and number was altered and they will not mesh properly if they are mixed

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Old mechanics, one of whom was my Dad, used to say "never mix old with new gears, because they are not worn in to each other". They had no answer when I asked "Are new gears worn into each other?"

Of coarse, if the tooth profiles are different, one cannot/ should not mix old and new. As a poor college student, I mixed old with new (four wheelers) on many occasions with no ill effects, apart from blowing gears due to too much horsepower and too little gearbox.

As we say in Texas, "if i had my druthers, i'd druther have new matched gears. But if hard pressed, one can get away with mixing a new with a worn, but not worn out, gear.

Slick

_______________________________________________________________

"SERVICE RELEASE No. N.61

Use of Commando gears on earlier models motorcycles Atlas, Mercury, 650ss, 99, P11A, P11, GLS, N15.

Worldwide (Trade only)

Layshaft pinion 040284: mainshaft pinion 040422

Against orders for pre-Commando layshaft high gear pinion 040284 we supply part no. 061058.
Similarly, orders for mainshaft high gear pinion 040422 are met with 061057.

IT IS VITALLY IMPORTANT WHERE EITHER PINION IS REPLACED TO FIT THE NEW MATING PINION AT THE
SAME TIME. This means that 061057 and 061058 must always be fitted as a pair to ensure correct
mating. This is a reminder of information issued originally in 1966 by the Norton Matchless Service Department.

September, 1971."

_________________________________________________________

Edit "1966" may not be correct as the 1968 Commando parts book lists 040284/040422.

The third gear pair changed 1970-on.

Mainshaft 3rd.
-'69: 040012
'70-: 040635

Layshaft 3rd.
-'69: 040420
'70- 040634

_______________________________________________________

Higher ratio 2nd. gear pair, 850 Mk1A and later models.
Change of part number for 850 Mk2/2A sleeve gear due to the addition of a bush retaining groove (& circlip) at the outer end.
Change of 850 Mk3 sleeve gear part number due to the addition of a second bush circlip groove at the inner end.

puts into question this

https://www.accessnorton.com/NortonCommando/gearbox-identification.18335/#post-272950

The root thickness of the gear teeth was increased.
You can't mix gears of the AMC and AMC Mk2 gearboxes.
Thats why they always advise to only ever change gear PAIRS....

This wasn't for the Commando though, this was sometime in the early 1960s.
For the SS dommies, perhaps. Or as a result of (?).

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any further info on this part?

L.A.B. said:

this is a reminder of information issued originally in 1966 by the Norton Matchless Service Department.

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the service bulletin seems to cover one specific example of 2 new gears that must match, when fitting the 2 specific updated commando gears into older boxes

Use of Commando gears on earlier models motorcycles Atlas, Mercury, 650ss, 99, P11A, P11, GLS, N15.

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