Atlas barrels?

I'm after another set of Commando barrels for the follow on project. I saw these on Ebay...They've got a standoff flame ring, if that's the right word?

Not seen this before on a Commando set...Just wondering if they're off an Atlas, or something instead?

http://www.ebay.com/itm/Norton-Commando ... 9b&vxp=mtr


Cheers,

Steve

They are pre commando, spigoted barrels. the protrusion is called a spigot.

Ah, brill...Thanks for that bwolfie

Cheers,

Steve

Atlas models lost the spiggotted cylinders somewhere in the 1960s.
Anyone know when ? 1965 ??

Heads also come in spiggotted and then non-spiggotted versions...

P.S. All Norton cylinders were spiggotted up until this point. ?
Going back many decades....
(were navigators and jubilees etc ??)

Rohan, my 1967 Matchless G15 has non spigotted barrels. The other thing that makes them non Commando compatible is that the head bolts are a smaller diameter, although you could obviously redrill and tap the holes bigger as the spacing is I believe the same.

Did all atlas heads have those small headbolts ?

Rohan said:

Atlas models lost the spiggotted cylinders somewhere in the 1960s.
Anyone know when ? 1965 ??

Heads also come in spiggotted and then non-spiggotted versions...

P.S. All Norton cylinders were spiggotted up until this point. ?
Going back many decades....
(were navigators and jubilees etc ??)

Click to expand...

I had a 1965 Atlas that had spiggotted cylinders, so I cannot really confirm this. My information is that they were removed after the first batch of early Commandos, which at the time was still using Atlas engines, with the rev counter drive off the timing cover.

1965 was the last year that all heavy production got the spigotted cylinder, 500cc, 650cc and 750cc.

I have heard of re-drilling and tapping the Atlas cylinders with the 5/16 head bolts to take the 3/8" Commando head bolts, but if you look between the fins on both an Atlas and 750cc Commando cylinder you will see that the Commando cylinder had a lot of material added in there for the bigger head bolts to anchor in, the Atlas was pretty skimpy in this area.

The 500cc and 650cc engines had the 3/8" bolts just like the Commando, it was just the Atlas that had the small diameter head bolts.

It was a neat trick they did to convert the 650 to a 750, all they did was make a new cylinder and pistons and did some different machining on the 650 crankcase and head castings, some re-balancing of the crank and there you were. It was sort of a turd of an engine though, with more vibration and low compression and initially a single carb, it was supposed to be a docile touring bike with a broad spread of power, the same idea Norton had again later for the 850.

I have 1962 Atlas engine shop #2 which I want to restore someday and at least put on a stand.

Bernhard said:

I had a 1965 Atlas that had spiggotted cylinders, so I cannot really confirm this. My information is that they were removed after the first batch of early Commandos, which at the time was still using Atlas engines, with the rev counter drive off the timing cover.

Click to expand...

Thanks Ben for the 1965 info.

I had a late Atlas project engine that had spiggotted cylinders and non-spigot head, (which obviously cannot have come like this, they CANNOT be bolted together like that) so all the dates tie in...