650SS Head Gasket

KHK

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Dec 13, 2008
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I recently acquired a 650SS project bike, with a fresh bottom and top end.
I did not know that these older engines had spigots on the cylinder that protruded into the head, unfortunately my new engine has had these decked off. The head is correct for s 650, and the bore is a +40thou 68mm overbore, which leaves me with a little problem.

One idea I had is to make a steel ring to fill the head where the spigot was, however I would need a head gasket with a 68mm bore. I suppose I could make one, but I want to see if anyone been here before that could share a good solution?

Thanks,
Kris
 
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Nov 17, 2010
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It's not unusual for the spigots to crack & need to be removed in case any bits break off. I had a 650 SS that it happened to & I did nothing after they were removed. I used a solid copper gasket & used the bike for years & thousands of miles without a problem. Theoretically you are dropping the compression ratio a bit, but it is only a bit & I don't suppose you're looking to set any performance records on a 50 year old bike. I didn't notice any performance problems with mine & i was a teenager then so rode it hard & fast everywhere.

Ian
 
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Jan 21, 2011
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After a certain engine # the 650 Norton did not have the spigots anyways, so parts are out there for both early and late non-spigoted 650 Nortons.

AMC made available in their parts book, the rings to press into the old heads for those buying a new non-spigoted cylinder for their older machine with spigots.

I have this old head lying around which someone had installed the rings in, and which also someone has ruined the original finish on with bead blasting..... The rings are aluminum, probably not hard to make if you can not find some in stock somewhere.

 

KHK

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Dec 13, 2008
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Thanks for the insight, the ebay find is great,
It is preferred to have the gasket be closer to the bore diameter to avoid deposits building in that area,
 

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