cylinder head recognition

nimrod

nimrod

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Nov 4, 2020
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Hi all. I have just purchased a bundle of Norton parts, 2 questions, I have 2 cylinder heads, I believe 1 is commando and the other an Atlas. the only visual difference I can see is one bolt hole on 1 is larger, assume for 3/8 and the other is 5/16. number on 1 is 25166, and 25319 on other, maybe casting numbers. I have pics but can't load..
the other question is the Primary covers, apparently the Atlas is longer and Tin, BUT I have a P11 and a Mk3 1976 commando and offering the tape up, the commando sits about an inch longer and the P11 isn't tin??? I did read somewhere the Hybreds are different, is the Dominator the same atlas? as the P11. thanks in advance
 
Norton Heavy Twins Heads
David Comeau-Aug 2000-update- September 2016
The pictured heads try to show the evolution and the details of Norton heavy twins from 1950 through 1975.
Click to expand...

atlanticgreen.com/nhth.htm
 
nimrod said:
Hi all. I have just purchased a bundle of Norton parts, 2 questions, I have 2 cylinder heads, I believe 1 is commando and the other an Atlas. the only visual difference I can see is one bolt hole on 1 is larger, assume for 3/8 and the other is 5/16. number on 1 is 25166, and 25319 on other, maybe casting numbers. I have pics but can't load..
the other question is the Primary covers, apparently the Atlas is longer and Tin, BUT I have a P11 and a Mk3 1976 commando and offering the tape up, the commando sits about an inch longer and the P11 isn't tin??? I did read somewhere the Hybreds are different, is the Dominator the same atlas? as the P11. thanks in advance
Click to expand...
P11 primary is definitely alloy, shorter, and narrower inside than the Dominator and Atlas primaries. The alternator stator also mounts inside the outer primary case of a P11, not on the crank case.
 
I have now got to the gear boxes. again they look similar but the stubs/flange for the thru bolts appear to be different widths. The number stamped is NA9754 maybe (NA = Norton atlas???) any advice will be welcome. thanks N
 
Last edited:
nimrod said:
I have now got to the gear boxes. again they look similar but the stubs/flange for the thru bolts appear to be different widths. The number stamped is NA9754 maybe (NA = Norton atlas???) any advice will be welcome. thanks N
Click to expand...
The gearbox output shaft, the inner and outer cover
And the width of the gearbox top mount are different between a commando box and an earlier one
 
baz said:
The gearbox output shaft, the inner and outer cover
And the width of the gearbox top mount are different between a commando box and an earlier one
Click to expand...
am I rightt thinking the later one is narrower. I know they are different but its which way round there different.
 
nimrod said:
am I rightt thinking the later one is narrower. I know they are different but its which way round there different.
Click to expand...
The top mount of a commando gearbox is narrower to allow it to fit in the gearbox cradle
Once in the cradle a spacer is fitted to the top left hand side of the mount ,I believe the spacer is 3/16" thick from memory
 
nimrod said:
I have now got to the gear boxes. again they look similar but the stubs/flange for the thru bolts appear to be different widths. The number stamped is NA9754 maybe (NA = Norton atlas???) any advice will be welcome. thanks N
Click to expand...
Commando has longer mainshaft, at the clutch end, and obviously so.
 

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