G80CS / 1960: Barrels

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Location: 5550 HORDALAND, NORWAY

G80CS / 1960: Barrels

Postby mdt-son » Mon Aug 03, 2020 11:26 am

Hi gents,

How much can a G80CS barrel be bored to before the original liner integrity is compromised?
I read somewhere a liner thickness of 1.5mm is minimum.

TCS barrels have a liner OD of 94 mm and will allow rebores to 90+ mm.

With a suitable conrod and some machining, would it be possible to fit a G50 piston in a G80CS engine?

-Knut

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Posts: 234
Joined: Wed Feb 01, 2012 1:22 pm
Location: 5550 HORDALAND, NORWAY

Re: G80CS / 1960: Barrels

Postby mdt-son » Mon Aug 24, 2020 2:08 pm

Ken de Groome kindly advised on the barrel re-bore:

90mm is the absolute limit without re-linering. The top flange however,
gets very thin at this level and prone to breaking off.

---

I was wondering about the spigot. Norton twins are doing well without a spigot (the works deleted them in 1966), even in racing engines. I am tempted to abandon the spigot (need a steel ring to fill the recess in the cylinder head). Of course pre-tension is crucial. Spigots are troublesome in my view. I am not surprised of the G12's tendenca to blow head gaskets. It's near impossible to have sufficient compressive force on two concentric mating surfaces at the same time.

Your comments are welcome.

-Knut

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