Emgo pistons

84ok said:

https://www.britishbikebits.com/forged-pistons-omega-norton-commando-750cc#.WsBZzojwaUE

https://www.accessnorton.com/NortonCommando/piston-to-bore-clearance-for-omegas.15658/

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The ones being discussed in the second link you posted were NOS cast Omegas from the 70s. I couldn’t use them in the end cos they were std size and my barrel was slightly too big.

Omega are up there with the best in the world, the new forged Omegas are therefore as good as you can get for stock application IMHO.

No more excuses guys !!

rvich the head is far from buggered . all that has happened is that some time in the past the threads give up .At the time the head was machined and Duramilium insert were pressed in these are plain on the outside and threaded internally for the exhaust rose. these are then welded into place .Once dressed with the weld behind the fitted rose it is really not noticeable this was/is common practice done by such as Norman White . what has happened on mine is after somewhere in the region of 40 years after this repair was done on tightening the weld has cracked and the insert has just started to move it needs dressing back and re welding when done it will be invisible good for the next forty years and even the most judgemental sarcastic pedant wont even be able to pick me up on it Although he will go straight for the back light unit which is off a 69 A65

L.A.B. said:

No, AN pistons are GPM.

And "Omeag" (Omega?).

https://andover-norton.co.uk/
"Forged Omeags to our design with about 10.5:1CR!"
(850)

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OK Thanks...
Let me put the question another way... I have to replace my std. pitons as they have the slits cut for oil transfer under the scrapper rings.
Rather than recommendations for the best piston to fit.... which ones need to be avoided??
Irrespective or the piston manufacturer are the ring land dimensions all the same?... as I would like to fit "Hastings" rings