What year is this engine?

Slowtoo

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Apr 22, 2016
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Looking at a 1970 Norton with engine stamped N15cs 123916 . Having trouble deciphering what year and make it is. It looks like a Commando but numbers don't work. Thanks for any help. PS: Don't own a Norton now but I'm working on it. Thanks again.
 
Something occurred to me. Will a 1970 inner and outer primary cover fit the 1967 n15cs cases?
 
Slowtoo said:
Something occurred to me. Will a 1970 inner and outer primary cover fit the 1967 n15cs cases?
Click to expand...

Aside from rotating the mounting bolt pattern on the inner cover to align the Commando inner cover with the upright Atlas engine, the major problem is fitting the left footpeg. If the N15 is similar to the Atlas, the Commando inner and outer covers will need bores to fit and seal the footpeg mounting hardware.

Slick
 
Slowtoo said:
Looking at a 1970 Norton with engine stamped N15cs 123916 . Having trouble deciphering what year and make it is. It looks like a Commando but numbers don't work. Thanks for any help. PS: Don't own a Norton now but I'm working on it. Thanks again.
Click to expand...

Easy way to see if it still has the original Atlas engine, look at the timing cover –if you have your rev counter gearbox on the upper corner of the cover –it’s an Atlas engine rather than than the latter Commando.

http://www.bing.com/images/search?q=Nor ... ajaxhist=0

But this is a Commando;

http://www.bing.com/images/search?q=Nor ... ajaxhist=0
 
Slowtoo said:
Something occurred to me. Will a 1970 inner and outer primary cover fit the 1967 n15cs cases?
Click to expand...

Primary cases from what, as we don't actually know whether the cycle is "1970" or if it's a Commando? More detailed information and/or photos would be helpful?

Bernhard said:
Slowtoo said:
Looking at a 1970 Norton with engine stamped N15cs 123916 . Having trouble deciphering what year and make it is. It looks like a Commando but numbers don't work. Thanks for any help. PS: Don't own a Norton now but I'm working on it. Thanks again.
Click to expand...

Easy way to see if it still has the original Atlas engine, look at the timing cover –if you have your rev counter gearbox on the upper corner of the cover –it’s an Atlas engine rather than than the latter Commando.
Click to expand...


If it was a 20M3 Commando it would still have the timing cover rev counter drive, however, "123916" is too early for it to be a Commando engine, and it is apparently stamped 'N15CS', not '20' (Atlas), '20M3' (early Commando) or '20M3S' (Commando).
 
My G15CS/1235xx was dispatched in July 1967. Chances are the N15CS motor in question left the factory in July or August of 1967, too.

An Atlas motor can be fit into a Commando frame, especially a late 1967, as it came with a distributor and Amal concentrics. The first 3500 or so Commandos (1968 and early 1969) used the Atlas-style distributor and the tach drive in the timing cover, the same as the N15CS.

The head would need to be a Commando, or modified, as the N15 used Atlas-style rocker lubrication. Commandos moved the rocker feed to the sides of the head because of the different head steady. The Ni5 head is not cast with the proper boss on the side of the head for this modification.

Primary mounting is a little different, as the N15 used the AMC primary with Atlas clutch, but fitting a Commando primary is not difficult.

Balance factor is different between the two applications, but who's to say if the engine was re-balanced to the Commando balance factor?



Sounds like somebody blew a Commando motor 40-something years ago, and found another Norton 750 motor to replace it.
 
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