valve stem cups

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Chris Berry
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valve stem cups

Post by Chris Berry »

Have nearly completed the rebuild of my 1948 G80 engine and noticed that the hardened steel valve stem cups discussed in the manual are missing. On inspecting the old valve stems (I have had new valves and guides put in the head) there is wear on the top indicating that the cups have not been fitted to the engine prior to my purchase. I have ordered these cups from AMOC but am wondering if these are necessary with modern valves. Can anyone help on this?

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Rob Harknett
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Re: valve stem cups

Post by Rob Harknett »

?????????????????? I cant see how the valves will stay in place without the cups
Ashampoo_Snap_2017.04.28_10h32m49s_002_.png
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1608
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Re: valve stem cups

Post by 1608 »

Think Chris means valve stem caps, not cups.
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Rob Harknett
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Re: valve stem cups

Post by Rob Harknett »

Guess so John, I am sure valve stems got a bit longer when the cups were dropped.
Chris Berry
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Re: valve stem cups

Post by Chris Berry »

Rob Harknett wrote:?????????????????? I cant see how the valves will stay in place without the cups
Ashampoo_Snap_2017.04.28_10h32m49s_002_.png
Sorry Rob, I did mean the caps. Are they still necessary? I have just replaced the valves and guides with the ones available from AMOC but don't know if these are still required. I am assuming that they were used to reduce the wear on the valve stems themselves
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clive
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Re: valve stem cups

Post by clive »

better tell us what valves you ordered. You can fit earlier or later valves to your head. You will only need valve caps if you have the eariler type. They were used because the original early valves did not have a harden stem.
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Chris Berry
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Re: valve stem cups

Post by Chris Berry »

clive wrote:better tell us what valves you ordered. You can fit earlier or later valves to your head. You will only need valve caps if you have the eariler type. They were used because the original early valves did not have a harden stem.
Thanks Clive, the valves hat i have now installed in the head are part No. 013989 purchased from the AMOC site. The inlet and exhaust valves are the same part No. That's about all I know about them

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clive
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Re: valve stem cups

Post by clive »

the parts you have fitted are for 49-59 and require no valve caps. They will work fine in your engine (but without the valve caps).
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Re: valve stem cups

Post by 1608 »

Am I missing something here, usually do mind! Both valves may or may not be the same size, but the exh and i/l valves are not the same material. Try offering a magnet to each valve and you will find that the exh valve is not attracted to the magnet. An i/l valve would not last long if fitted in the exh port.
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Rob Harknett
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Re: valve stem cups

Post by Rob Harknett »

clive wrote:the parts you have fitted are for 49-59 and require no valve caps. They will work fine in your engine (but without the valve caps).
The correct valves STD676 & STD 677 would be new part number 000676 & 000677, so it does indeed look like you have valves that will not use the caps . Perhaps you will see the new valves you have here longer than the old ones.
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