Mark 2 vs Mark 3 frames

Could somebody please tell me the differences between a Mark 2 and a Mark 3 frame?
How complicated is it to hang Mark 2 bits on a Mark 3 frame?
Is it relatively easy to modify a Mark 3 frame so that Mark 2 bits fit?
Thanks.

Stephen Hill

There's a hook to hold the rear brake when you are working on it. There's a seat hinge mount point too. Fork yolk swing stuff lock too. Rear rail bracings too. :wink:

The only difference in the frame between Mk2 (850) and Mk3 is the rear loop bracing, which also incorporate the hole for the seat lock. You can use a Mk3 frame to replace a Mk2 with no modification. It will be easily identified as a Mk3 by the seat lock hole however, so it is not a transparent swap.

I was told the Mark 3 frame has different stops to work with the Mark 3 triple trees. Can anybody explain these differences?

Stephen

Ron L said:

The only difference in the frame between Mk2 (850) and Mk3 is the rear loop bracing, which also incorporate the hole for the seat lock. You can use a Mk3 frame to replace a Mk2 with no modification. It will be easily identified as a Mk3 by the seat lock hole however, so it is not a transparent swap.

Click to expand...

I believe the steering lock tab(s) welded to the steering tube are different between MK III 850's and earlier 850 models. I think on my '74 it's a flat piece of steel, and on MK III bikes it's thicker with a slot for the steering lock pin to drop into. I am unsure how the difference might affect the functionality of the steering locks if one were to swap triple trees between the models.

On John Player Nortons, it's a flat piece of steel with two short arcs clipped from the ends.

I suppose it's possible, too, that some pre MK III 850's were fitted with the MK III style of steering lock lug. Just speculation on my part, though.


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Torontonian said:

There's a hook to hold the rear brake when you are working on it. There's a seat hinge mount point too. Fork yolk swing stuff lock too. Rear rail bracings too. :wink:

Click to expand...

Isn't the hook just a plastic covered piece of steel that fits around the rear frame loop? Similar to the brackets that hold the grab bar on? There's nothing welded on, is there?

Pre-Mk3 850
https://andover-norton.co.uk/en/shop-dr ... pair-items
The original pre-Mk3 steering lock plate was different although it seems AN now supply the Mk3 plate.

Mk3
https://andover-norton.co.uk/en/shop-dr ... pair-items

Stephen Hill said:

I was told the Mark 3 frame has different stops to work with the Mark 3 triple trees. Can anybody explain these differences?

Click to expand...

There's no apparent difference as far as I can tell, the frame stop (1) and yoke stops (2) appear to be the same.

Torontonian said:

There's a hook to hold the rear brake when you are working on it.

Click to expand...

It's a clip, not part of the frame.
https://andover-norton.co.uk/en/shop-de ... er-support

There's no apparent difference as far as I can tell, the frame stop (1) and yoke stops (2) appear to be the same.

Click to expand...

The repair part for the steering lock is the same as the MK3 one will work as a replacement and is more robust, but a 72 frame not repaired has a different bracket (and pretty sure my 74 is the same as the 72 but can't get to it.), the yoke stop is the same.



If you look at the repair parts for the 71 onwards frame AN have also standardised on the longer inner rear suspension plate, whereas to be 100% correct they should have offered the short one, but who would not want the longer one to stop the rear frame loop drooping.


06.4282
FRAME R/SUSP. MOUNT PLATE



So the repair parts are not 100% correct for every frame they are said to apply to.

kommando said:

If you look at the repair parts for the 71 onwards frame AN have also standardised on the longer inner rear suspension plate, whereas to be 100% correct they should have offered the short one, but who would not want the longer one to stop the rear frame loop drooping.

So the repair parts are not 100% correct for every frame they are said to apply to.

Click to expand...

Also, the "71-on 06-5404 frame" is the (28 degree) '850' frame. :?

L.A.B. said:

kommando said:

If you look at the repair parts for the 71 onwards frame AN have also standardised on the longer inner rear suspension plate, whereas to be 100% correct they should have offered the short one, but who would not want the longer one to stop the rear frame loop drooping.

So the repair parts are not 100% correct for every frame they are said to apply to.

Click to expand...

Also, the "71-on 06-5404 frame" is the (28 degree) '850' frame. :?

Click to expand...

May also present an issue to those with 'S' Type exhausts as the bracket clamps to the outside of the top shock mount...

Agree it's a good modification to have otherwise.