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650ss barrel spigot cracked

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Hi,

Does anyone have any experience/advice on converting spigoted barrels to spigot-less?

I have a set of barrels which are +60 thou oversize, resulting in a thin spigot wall. Sadly one spigot has a circumfrential crack around approx one third of the circumfrence. Also the mating face of the barrel is pretty rough looking, and not flat.

I'm considering having the spigots machined off and the mating face very lightly skimmed to clean it up. I understand that in the past Norton produced some ring insets to fit to the head in place of the spigots.

Anyone have any info on these inserts, or experience of their use.?

Thanks for reading

Alex

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hello  all now 650cc barrels were never meant to be bored out to 60+ over size  in the first place  the recommendations are for 650cc barrels to be only bored to 40+  and then re-sleeve  the barrel is what you need to do in this time round  ,   Yours  Anna j

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Hi,

When I stripped the engine of my Atlas (bike bought 'restored' from a club member, but badly bodged), I found I had a spigot type head, and matching composite head gasket, but spigotless cylinders.  Unsurprisingly, the  gasket had blown at the narrow sealing land between the combustion chambers.  A copper gasket would likely have fared better, but I did not elect to try that.

Norman White offered to fit adaptor rings in the head recesses, which apparently used to be quite common practice, but I then found a spigotless head, which was also in better condition, so used that.

So for you, an option would be to machine off the spigots and fit adaptor rings to the head?

Regards, Andy

 

 

 

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My 650SS has a Spigotless Barrel and a spigot type Head. I fitted the alloy adapter rings ( RGM) and Loctited them in.  No problems as long as you fit  the spigotless composite head gasket, other wise they'll be in bits and down your exhaust pipes in next to no time! ( don't ask how I know! )

Thanks for the info Anna., but I think I will try and use what's there for now as the engine has done very little since being rebuilt about 30 years ago. Pistons, rings and bores almost unmarked, and it's not going to be subjected to heavy use.

Thanks for the info on the inserts folks, got to be worth a try, and if it goes wrong I'll just have to have the cylinders re-sleeved.

Thanks for the help

Alex

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Hello Now for early 650cc pistons where BHB 23268 lh and 23269,rh  or 23270 rh and 23271lh  cylinder barrel Norton number 23263,   

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Hello Anna

My barrels have a number 22710. Is that a part number or just a casting number?

No manufacturers name on pistons, just a casting number 308.

 

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If you search here, someone posted a picture of his wrecked piston complete with a metal 'worm' in the chamber. It was the remnants of a filler! How filler rings fit is a mystery to me. Tolerance on thickness should be exact, shouldn't it? No wonder they reportedly escaped on that occasion.

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Well, in discussion with several others confronted with this problem, the consensus seems to be that you can machine the spigots off, and then use a solid copper gasket. You can have inserts fitted to the head to fill the volume occupied by the spigots if you are precious about your compression ratio, but as my cylinders are +60 thou the volume of the remaining spigots is just 1.63cc, which increases the unswept volume from 35.9cc to 37.53cc. Given that the overbored swept volume is now 337.64cc, this results in a compression ratio of 8.99.

 

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