1975 Norton Mk3 distinguishing features

p400

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What are the subtle differences between a Roadster and an Interstate Mk3?
I can see the gas tank and side covers .
Amals, instruments, seat, chassis, horn, fenders, wiring, handlebar, etc ??????

fork spring rate?, rear spring rate?, rear dampers?

Has anyone done a run thru the parts manual to get anal about this?

Thank you


1975MklllInterstate.jpg
 
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L.A.B.

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What are the subtle differences between a Roadster and an Interstate Mk3?
I can see the gas tank and side covers . Amals, instruments, seat, chassis, horn, fenders, wiring, handlebar, etc ??????

Tank, seat, side covers.
Handlebars were optional. Interstates generally had Veglia instruments and Roadsters had Smiths (since 1973 when Veglias were introduced). Minor differences between early and later Mk3 wiring but this applies to both Roadster and Interstate.

Grab rail 06-4978 is now the same part for both Interstate and Roadster. (Edit: Although AN is currently offering the previous different version grab rails for Mk3s instead of 06-4978 :rolleyes:)



fork spring rate?, rear spring rate?, rear dampers?
No.
 
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Deets55

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3B7CBE9F-15DD-48F9-8922-21A094CB16B3.png
Old Britts also shows three different grab rails for the MKIII. I believe the Interstate is a little more vertical. Not sure if this is OEM or not just caught my eye when I was parts shopping a while back.
Pete
 

L.A.B.

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Old Britts also shows three different grab rails for the MKIII.
One of the three is the Hi-Rider grab rail.

Presumably, the other two they sell are AN parts so it saves AN producing three similar versions of grab rail (06-3819, 06-3632 and 06-4978) however, the Old Britts list has 06-4978 as "Interstate". That should be 06-3632 as 06-4978 is the standard Roadster/Interstate grab rail.

The single Mk3 grab rail (Group 28, item 26) having become two different parts 26A and 26B.
https://andover-norton.co.uk/en/shop-drawing/149/seats-seat-fittings-grab-rails

https://andover-norton.co.uk/en/shop-details/16158/grab-rail-roadster-
https://andover-norton.co.uk/en/shop-details/16124/grab-rail-interstate-

Edit: (The change to the "commonised" 06-4978 grab rail is the subject of Norton Service Release N3/54, May 1973.)
 
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Here is a picture of a 06-4978 "universal" grab rail which was introduced sometime during 1974 on the Mk II and Mk IIA and also used on the Mk III's. This grab rail was used on both Interstate and Roadsters.

A couple identifiable differences between this and the earlier type grab rails are that the base of this grab rail is shorter and it is also straight at the base. Also the mounting brackets are U-shaped and require longer bolts for mounting.

I hope this is of some help.






Peter Joe
 

p400

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What is the proper key set for a 1975 MkIII?
I think I see a seat lock, steering lock and ignition.
One for all?
What does the keyhead look like? picture?

number stampings on key? picture?

Page5-6LockQ.jpg
 

Deets55

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Mine has a different key for each lock.
My grab bar is similar to the one pictured above with the “U” shaped mounting lugs. Not sure what the other one looks like.
Pete
 

L.A.B.

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What is the proper key set for a 1975 MkIII?
I think I see a seat lock, steering lock and ignition.
One for all?
Seat and ignition are the usual Wilmot Breeden UNION FS type key.

Mk3 steering lock is Neiman.


What does the keyhead look like? picture?
Union:
https://www.ebay.ie/itm/Lucas-NOS-3...ic-Mini-etc-/202585948686?hash=item2f2b10420e

Neiman:
https://andover-norton.co.uk/en/shop-details/16522


number stampings on key? picture?
'FS' and 3-digit code number.
 

p400

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Thank you both very much.

Where are details, in literature, to explain the accessories plug to run a shaver and/or 12v item please?

Watts available, possible fusing, limitation?

Is there a Norton shaver?

Page4.jpg
 
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What is the proper key set for a 1975 MkIII?
I think I see a seat lock, steering lock and ignition.
One for all?
What does the keyhead look like? picture?

number stampings on key? picture?

View attachment 8417

Big fib re the new exhaust. They claim it increased power. In truth it killed the top end and harmed midrange as well.

Glen
 

p400

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Will the ignition and seat lock match?
Is this the correct keyhead?
or are there variations?


BreedenFSStamp.jpg
 

Deets55

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As Les stated both ignition and seat are FSxxx, but have different cuts, so they are not interchangeable. Steering lock is a Neiman steel key. I should have been a little clearer in my response when I said three different keys.
Pete


EDIT. Just saw that last question about key head. My ignition has a round head, my seat has a square head (like you have shown). I suppose a locksmith could re-pin either lock to match the other. Steering lock is an entirely different animal.
 
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p400

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So this is it? No Norton shaver?

What is the plug type ? Some Lucas standard or sumthin else?


Power take off socket
A pIug and socket, mounted on the right
hand side of the battery tray, provides 12v
at a maximum of 17½ amps for accessories,
such as a radio or shaver, or may be used
for battery charging. When appropriate,
ensure that the plug is wired with the
correct polarity. On this motorcycle, the
positive, indicated by a red wire, is
earthed (grounded).

PowerTakeOffSocket1.jpg


 
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p400

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This ignition key, shown in this brochure, is showing a squarish head.

Do both Union keys, ignition and seat, have the same grooving, and number of cuts?


 

Deets55

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Yea that power take off is an interesting conversation piece. The thing to be aware of is that it is not fused separately. If it accidentally gets shorted the main fuse will blow and the bike won’t run till the fuse gets replaced.
Pete
 

L.A.B.

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Do both Union keys, ignition and seat, have the same grooving, and number of cuts?
both ignition and seat are FSxxx, but have different cuts, so they are not interchangeable.
Ignition and seat keys of mine are also grooved and cut differently or they would be if I'd been given a seat lock key and I didn't get a steering lock key either but the Neiman steering lock blank fits the seat lock.
 
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