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Model 50 rear swing arm & gearbox mounts vs ES2

Submitted by simon_amos on Thu, 05/05/2011
Forums
Singles

Hi guys,

I have the pleasure of rebuilding a classic model 1958 model 50 for a friend, and have some questions.

The machine arrived as a rolling frame, with a 350cc single engine - the engine number contains N 13, I believe this indicates a 1958 model 50.

The frame howeveris a simplex, and the number contains J 4 - I believe this indicates a 1954 ES2.

1. I was also given the model 50 frame, which matches the engine number (desireable), but the mounting brackets for the gearbox, and rear swingarm mountings are different - is this due to the model 50 vs ES2?

2. Are the gearboxes different between the model 50 and ES2?

3. How do I identify the gearbox manufacturer AMC etc?

4. Are the mounts interchangeable?

5. Where could I get the correct rear swingarm, so I can build the machine with matching numbers?

Photos below

Model 50 swingarm, with gearbox support bracket studs at both sides

[IMG]http://i560.photobucket.com/albums/ss43/ianhendy50/DSCN5596.jpg[/IMG]

ES2 swingarm location, with gearbox support studs on LHS only.

[IMG]http://i560.photobucket.com/albums/ss43/ianhendy50/DSCN5598.jpg[/IMG]

All advice greatly appreciated.

Thanks,

Ian.

Submitted by ian_macdougall on Sat, 07/05/2011

Permalink

Hi Ian,

The frame differences that you see come from the year of manufacture and not from the model number.

Your 1954 frame will havethe forged engine cradle that came through from the earlier rigid & plunger frames. In54 the gearbox would have been the Norton "laydown" type, as in your photo. All the models (50, ES2, 19S) used the same frame and gearbox.

In 57 (I think) the simplex frame wasredesigned with tubular engine cradle and modified rear gearbox mount/swing arm pivot brace. The gearbox changed to the AMC type along with a new clutch. Again all the models from the period used the same frame and gearbox.

The AMC box has a rounded triangular shape with a circular cover to access the clutch cable. If you want to see one just look at a featherbed Dominator.

I think it is possible (please correct this if wrong) to fit a laydown box in the later frame and the AMC box in the earlier frame but you have to use therear gearbox plates to match the frame.

In your case you appear to have most of the parts to rebuild as a 54 model soyou should not have to worry aboutcompatibility between years.

Hope this is useful

Ian McD

Submitted by simon_amos on Sat, 07/05/2011

Permalink

Previously wrote:

Hi Ian,

The frame differences that you see come from the year of manufacture and not from the model number.

Your 1954 frame will havethe forged engine cradle that came through from the earlier rigid & plunger frames. In54 the gearbox would have been the Norton "laydown" type, as in your photo. All the models (50, ES2, 19S) used the same frame and gearbox.

In 57 (I think) the simplex frame wasredesigned with tubular engine cradle and modified rear gearbox mount/swing arm pivot brace. The gearbox changed to the AMC type along with a new clutch. Again all the models from the period used the same frame and gearbox.

The AMC box has a rounded triangular shape with a circular cover to access the clutch cable. If you want to see one just look at a featherbed Dominator.

I think it is possible (please correct this if wrong) to fit a laydown box in the later frame and the AMC box in the earlier frame but you have to use therear gearbox plates to match the frame.

In your case you appear to have most of the parts to rebuild as a 54 model soyou should not have to worry aboutcompatibility between years.

Hope this is useful

Ian McD

 


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