Trans Cradle Differences

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The picture in the shop manual is a 75 electric start because of the two locking bolts for the swing arm pivot. As I stated earlier both of the cradles in your first photo are correct for a 73. The last photo you posted is from an earlier bike as it does not have the oil filter mount holes.
 
Here is why it’s confusing. Here is a cradle on eBay. It says it’s for a ‘75. There are the two little holes for the filter, but the swing arm is not the reinforced swing arm.

I have to guess that even though they beefed up the 850 swing arms in ‘73 and beyond, the 750 swing arms stayed the same even though the cradles changed.

Trans Cradle Differences
 
The 75-850 e-start cradle and swingarm like the last picture is a one year item.
The trans mount holes are not slotted for chain adjustment.
The swingarm is built with larger tube diameter and for use with a rear disk brake.
It is not what you want.
 
comnoz said:
The 75-850 e-start cradle and swingarm like the last picture is a one year item.
The trans mount holes are not slotted for chain adjustment.
The swingarm is built with larger tube diameter and for use with a rear disk brake.
It is not what you want.
Click to expand...

Ok, so there are even more subtle differences. I need the cradle WITH the two little oil filter mount holes AND the slots for the chain adjustment.

Now I think I’m clear...

Than you!
 
'750' swingarm (without gussets x2 but can be welded in):
https://andover-norton.co.uk/en/shop-details/15269/swinging-arm-without-gusset-

'850' (73-74) swingarm with gussets as standard:
https://andover-norton.co.uk/en/shop-details/16319/swinging-arm-with-gusset-reinforcement-
Edit: There are two slightly different versions to suit either the early or late 'sealed' Mk2/Mk2A swingarm pivot assemblies.

'850 Mk3' box-section cross member and larger diameter tubes (for disc brake).
https://andover-norton.co.uk/en/shop-details/16662/swinging-arm-850-mkiii-06-5270-
 
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The hole you are struggling with may be the primary chain case central stud.
 
"I'm struggling with this one!"

= Inner primary case support stud.
 
Thanks guys, I knew someone would help me out. It's still too early here!
 
RGM Motors sell a Pre-MK3 cradle, but fitted with the two cotter pin fixing method for the swinging arm spindle.
I fitted one about 32 years ago - no problems to date !
 
Staytite said:
RGM Motors sell a Pre-MK3 cradle, but fitted with the two cotter pin fixing method for the swinging arm spindle.
I fitted one about 32 years ago - no problems to date !
Click to expand...

That would be a sweet way to go.

If the Mk3 cradle was modified for a gearbox adjuster, would it fit in all other apsects?
 
Shouldn't there also be a hole for the center stand spring?
 
rvich said:
If the Mk3 cradle was modified for a gearbox adjuster, would it fit in all other apsects?
Click to expand...

As the Mk3 RH gearbox hole shape is different, cutting the RH slot puts it close to the edge of the hole.
The hole for the adjuster would have to be raised slightly.
The Mk3 cradle has 3/8" lower engine mounting bolt holes instead of 5/16".
The hole in the LH plate for the Mk3 gearchange cross shaft is where the pre-Mk3 primary support stud would normally be.

maylar said:
Shouldn't there also be a hole for the center stand spring?
Click to expand...

Yes, but left side only.
 
Norcoastal said:
Here is why it’s confusing. Here is a cradle on eBay. It says it’s for a ‘75. There are the two little holes for the filter, but the swing arm is not the reinforced swing arm.
Click to expand...

From what I can see this is a Mk3 cradle, a Mk3 swinging arm (yes, it's reinforced), the correct spindle c/w welch plugs, and the adjustable rear ISO as fitted on the Mk3.

I am not sure what your objective is. If you want a faithful rebuild of your '73, then look for the appropriate parts for that model year. However, if you want to create the best Commando, then go for the above parts.

Now is the time to decide what kind of primary drive to fit. If you're staying with a triplex chain primary drive, the '73-74 cradle is appropriate. However, if you consider fitting a belt drive, the Mk3 cradle is the better solution, even when using the pre-75 primary covers, and fitting a belt drive tensioner HD style would give you the best set-up, see Old Britts for details.

You will probably want to fit the Mk3 style isolastic support in your cradle. No modification of the '73-'74 cradle is needed, however the pre-75 front engine mount needs to be altered. Furthermore, fitting so-called Kegler clamps is recommended when using the '73-'74 cradle which eliminates the rocking motion of the rear wheel when subjected to lateral forces, see
http://www.hollandnortonworks.eu/en/exclusive-commando-parts
. Alternatively, you may fit this cradle as cited above:
https://andover-norton.co.uk/en/shop-details/16872

-Knut
 
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mdt-son said:
You will probably want to fit the Mk3 style isolastic support in your cradle.
Click to expand...

I doubt Norcoastal has gone into that yet.


mdt-son said:
No modification of the '73-'74 cradle is needed, however the pre-75 front engine mount needs to be altered.
Click to expand...

The pre-Mk3 front mount does not have to be modified if the pre-Mk3 vernier conversion kit (or Hemmings kit) is used.

https://andover-norton.co.uk/en/shop-details/17047

mdt-son said:
Alternatively, you may fit this cradle as cited above:
https://andover-norton.co.uk/en/shop-details/16872
Click to expand...
Edit: Finding one of those in used condition, however, is unlikely.
 
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