Valve springs...

Bob Z. · Jan 1, 2013

I've disassembled a 750 head that has been in storage for a long time.

The valve springs had an interesting extra piece that maybe someone could add some information?
The valve spring top keeper is some exotic metal. The rocker arms have been beautifully lightened.

The head does not have a 'C' stamp, has 32mm intake ports, 38mm intake valves, the head gasket surface has not been shaved.
If I can remember correctly the head came off of a Dunstall 810 barrel.

Anyone else seen this third spring?

Rohan · Jan 1, 2013

Can't help at all, but it sure looks interesting. Duntall owners may know of it ?
Safety net for broken valve springs ??

What does the combustion chamber look like ?

Dances with Shrapnel · Jan 1, 2013

I believe the flat coil is a harmonic damper for the valve springs. Seen these before but never on a Norton.

sidreilley · Jan 1, 2013

I have seen these in performance valve springs from (auto) cam grinders before, but not in motorcycles. I believe it is there to cut transfer of harmonic vibrations between/in the regular springs.

Bob Z. · Jan 1, 2013

Thanks,
After further dis-assembly I found oil seals fitted on the exhaust valve guides and all rockers are shimmed to center over the valve stems.

The un-shaved head has the letter 'A' stamped on the casting blob under the exhaust port.

Perhaps an economy performance upgrade way back in the past.

comnoz · Jan 1, 2013

I have an OLD box of S&W performance valve springs for a Norton that look just like those. Ti retainers and all.
The flat spring is a damper. When it rubs on the coils it helps stop the spring surge and bounce. Jim

Hobot · Jan 1, 2013

Might consider searching up 'valve spring heating' for insights on rubbing friction as most cause of spring heat and temper loss threshold plus the recent thread here on head oil flow and drain subject. The new age way to go is with Jim Schimdt's bee hive springs, if wanting to really kick up Commando heels on cam.

Rohan · Jan 1, 2013

I fitted S&W valve springs to an 850 head, quite some while ago.
I vaguely thought they were triple valve springs ?

What has happened to S&W, they disappeared quite some while ago.
Who makes comparable good valve springs these days ?

lcrken · Jan 1, 2013

S&W (not to be confused with British W&S springs) went out of business over 30 years ago. R/D springs started up in 1981 to fill the vacuum S&W left, and I think it was started by a former S&W employee. They have had a very good rep with engine builders ever since. They still offer the Norton spring kit with titanium retainer. I've used them for years, and believe them to be the best available conventional design spring for Commando racers.

http://www.rdvalvespring.com/

Ken

Bob Z. · Jan 1, 2013

Here is a photo of the intake side.
Note the shimmed rocker arms.

Valve springs...

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