Flange ring

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Jul 11, 2010
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Just about to start to rebuild my 650 Manxman motor but the flange ring on top of the cylyinder one side has a bit broken off the ring



what will I need to do to fix this or do I have to resleeve the barrels or can I use it this the way?
The bores on this motor is still good at 20thu over size.

Ashley
 
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Aug 26, 2010
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Remind us where this motor actualy seals its head/cylinder joint.
The flange plays no part in the actual sealing ?
The head gasket should start to crush before the flanges touch the head. ?

On the earlier 500cc dommies, its the headgasket between head and cylinder that does the sealing, the flange merely positively locates the head to the cylinder.
On subsequent domies, somewhere in the mid1960s, that flange was deleted - the headbolts did all the locating, with no ill effects it seems.
Makes surfacing the top of the cylinder much easier - which you are going to need to do ?

You do see reports of those flanges being totally machined off.
Although metal rings then need to be fitted into the head to substitute, and remove what would otherwise be a dead space in the combustion chamber.
 
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I intend to shave the spiggotts off some Atlas cylinders, and use them with a later head.
As many have found, if they serve no real purpose, there is no need to keep them...
 
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Feb 28, 2012
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Rohan said:
I intend to shave the spiggotts off some Atlas cylinders, and use them with a later head.
As many have found, if they serve no real purpose, there is no need to keep them...
Gidday Rohan
I was talking to a bloke on Saturday who said he had done the same thing. Put a Commando head on Atlas barrels. he pointed out the Atlas cylinder has the 4 outside holes tapped 5/16th diameter and Commando 3/8th holes. he just puts 5/16 head bolts into the 3/8th holes. and also of course got rid of the flanges.
Not knowing Atlas motors, is this correct. also is there any consequences from putting the smaller bolts in the bigger holes
ride safe Bradley
 
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Nov 18, 2005
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I'd machine it off and insert a ring into the groove in the head.

My Commando/Atlas motor was the opposite of yours.... I had an Atlas head with Commando barrels. So I had no flange on the barrels I had but the grooves in the head where the flanges were supposed to go. I had a machine shop make a couple of alloy rings that are an interference fit in the grooves in the head. The head bolts do a perfectly good job of locating the head on the barrels.
 
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