Valve spring free lengths on 1960 M31

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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sjr
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Valve spring free lengths on 1960 M31

Post by sjr »

Just checking while the motor is down, the outer springs are 60mm. However, according to F. Neill's book for the '55 to '65 twins they should be 1 3/4" i.e. 44.45mm.

Is F.N. making a mistake, if so what should they be?

Grateful for the correct info.

Steve
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1608
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Re: Valve spring free lengths on 1960 M31

Post by 1608 »

If an M31 post 1960 is a twin then according to the manual the inner should be 2.030" and the outer 2.523" free length.

What does the M stand for, is it a standard AJS 31 650.
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sjr
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Re: Valve spring free lengths on 1960 M31

Post by sjr »

Yes it is, M=model
Thanks!
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1608
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Re: Valve spring free lengths on 1960 M31

Post by 1608 »

I gathered that much, but how does it differ from a standard AJS 31. What does the M mean?
By the way, as you probably know, too longer springs can become coil bound and too strong can cause premature cam/follower wear. Hope this isn't teaching egg sucking.
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Rob Harknett
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Re: Valve spring free lengths on 1960 M31

Post by Rob Harknett »

m= model
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Duncan
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Re: Valve spring free lengths on 1960 M31

Post by Duncan »

Some not so serious questions:

Didn't M used to equal Magneto?

If M equals Model what does G equal?
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Re: Valve spring free lengths on 1960 M31

Post by robcurrie »

Duncan wrote:Some not so serious questions:

Didn't M used to equal Magneto?

If M equals Model what does G equal?
...and what do 31 and 12 mean?

Rob C
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sjr
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Re: Valve spring free lengths on 1960 M31

Post by sjr »

1608 wrote:If an M31 post 1960 is a twin then according to the manual the inner should be 2.030" and the outer 2.523" free length.

What does the M stand for, is it a standard AJS 31 650.
Thanks! can you tell me which manual, and which page?
My F. Neill "Service and Overhaul Manual for the AJS & Matchless Twin Motorcycles" gives 1 19/32" inner and 1 3/4" outer on page 81.

Yes its standard with some deluxe items, magneto/dynamo motor.

Steve
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1608
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Re: Valve spring free lengths on 1960 M31

Post by 1608 »

The manual is the photo copy ( as supplied from the club ) from the original, page 15. A copy is available in the archives
section.

http://archives.jampot.dk/book/Workshop ... models.pdf
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