1962 and 1963/64 crankcases - differences?

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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1962 and 1963/64 crankcases - differences?

Postby mdt-son » Fri Aug 09, 2019 1:55 pm

Hi all,

The machining done at 1963 timing side crankcases changed to accommodate the high-capacity oil pump. For 1964 there was another change to the oil pump carrier, and I guess some oilways in the timing side crankcase are affected. Has anyone modified a 1960-62 crankcase to the later version, or knows how to accomplish this? What were the changes actually?

-Knut

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Re: 1962 and 1963/64 crankcases - differences?

Postby ajscomboman » Fri Aug 09, 2019 7:44 pm

Not aware of any changes to the crankcase other than relocating the PRV valve from the case to the pump body. Certainly no machining needed to fit the high capacity pumps only a deeper timing cover fitted with longer screws to allow fitting.

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Re: 1962 and 1963/64 crankcases - differences?

Postby JEAN-NOEL » Sun Aug 11, 2019 8:43 am

Yes, I agree with Rob.

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Re: 1962 and 1963/64 crankcases - differences?

Postby mdt-son » Mon Aug 12, 2019 12:19 am

Thank you, Rob and Jean-Noel. I am on a learning path re. the twin's oiling system!

A schematic drawing would have been really helpful. Is there one somewhere?

Regards,
Knut

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Re: 1962 and 1963/64 crankcases - differences?

Postby Yves.Astein » Wed Aug 14, 2019 8:10 pm

Hi Knut,

I dont know how far your understanding goes so far, but for beginners I might be able to help a bit.

the Oil ways are not that difficult.

Have a look here:

http://archives.jampot.dk/book/Owners_manuals/1957_=M=_Twins_Manual.pdf

On Page 21 and 23. Together with the explanation on Page 11 you should be able to understand the general paths of the Oil.

Its for G11 but I have had my G12 engine apart multiple times and I looked at all the Pathways, and I would say that the drawings look very simular to what I have seen in real.

You might also want to get your self a copy of
Roy H. Bacon
Matchless and Ajs Restoration: All Post-War Road Singles and Twins https://g.co/kgs/HExz1J

He explains in great detail about the Changes during production.

But as the much more experienced experts have already written above, so far I haven’t read anything about major changes to the cases except for the pressure relief valve...

Cheers Yves





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Re: 1962 and 1963/64 crankcases - differences?

Postby SPRIDDLER » Wed Aug 14, 2019 8:49 pm

A quick look at the 'Year by Year changes' for Twins in the Tech Articles library doesn't show any c/case mods 62/63/64.

http://www.jampot.com/article_read.asp?id=20
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Re: 1962 and 1963/64 crankcases - differences?

Postby ajscomboman » Thu Aug 15, 2019 6:16 am

The only other change I can think of other than the PRV is the increase in stud diameter for 63 models excluding the CSR is to 3/8" studs.

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