Author Topic: Valve Springs - possible source?  (Read 1197 times)

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Offline Hamwic

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Valve Springs - possible source?
« on: 04 Oct 2020 at 20:39 »
I have been looking for some valve springs for the M32 to replace the soggy and mis-matched items that were fitted. Here is some information that I have turned up.

AJS Matchless have an archive with, amongst other things, a W.G.James Valve Spring Catalogue.

The size given for the Douglas S6  is given as 1 7/8" long (47.6mm), ID 53/64" OD 1 7/64" (21/28mm) with 8 coils.
W.G. James part number is 150, but no Douglas part number is given. This matches two of the springs I have.

Very close in size to this is a Royal Enfield part no 150097. These are 2" (50.8mm) long x 1 3/32" (27.8mm) diameter, with 7 1/2 coils. (W.G.James number is 460. )

These are available from Hitchcocks in the UK, so I have ordered up a couple of sets, and will see how they feel for rate etc.

Offline tck

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Re: Valve Springs - possible source?
« Reply #1 on: 05 Oct 2020 at 08:13 »
The real test is the valve seat pressure,that max lift is not coil bound, and that no harmonics are introduced (the last item is hard to predict)
I spent some time on Gold Star springs for my Vincent race bike
I built a simple spring pressure tester out of wood some 6mm all thread a yacht turnbuckle and a spring balance
You can always build up the spring seat isn't that what they did on the 90+ racers?
I was working to 120 lbs seat pressure for racing  perhaps 10-15 lbs less for road work would be a starting point unless someone knows the real figure?

Offline Hamwic

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Re: Valve Springs - possible source?
« Reply #2 on: 05 Oct 2020 at 10:41 »
Thanks TCK, I sense a measuring fixture coming on. Given the generally flimsy nature of things throughout the M32 design - especially the crankshaft, I shall aim for the lower end of your figures I think. I suspect that any exuberance with the throttle will just end in a disappointing "BANG" so racing revolutions aren't to be recommended. That said, neither is the destructive load of valve float.

It will be interesting to see how the new and old springs compare, albeit the existing ones are probably coming up to 90 years old, so well past their best.

Offline tck

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Re: Valve Springs - possible source?
« Reply #3 on: 05 Oct 2020 at 11:35 »
Well at least you dont need an 8-1/2 ton jack to release them as I did on my 90+ heads!

Offline Hamwic

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Re: Valve Springs - possible source?
« Reply #4 on: 07 Oct 2020 at 11:04 »
The Enfield valve springs arrived today and dimensionally they are similar if a little over-long. After a couple of squeezes they settle down a little, so I expect them to settle more in service. They are/were made by Terry for the 350 SV Enfield, and the Terry number is V60.

The installed height on the M32 is 34mm, so a quick and dirty test using the scales and a 34mm spacer shows the installed pressure to be about 55lbs. The best of the old springs shows as 52lbs.

Both become coil bound at 1" fully compressed.

Apparently 50lbs is a figure suitable for flat head Fords and should be OK up to 5000 rpm they say. That being the case, I shall go with these, as I think 5000rpm would be a big, and final, day out on this particular machine. They are no worse, and perhaps a shade fresher than the existing set.