AJS & Matchless Owners Club

Hi, I'm restoring a 1960 650 G12.
Has anyone got a spare set of the above I could purchase. The heads I have are off the 1959 650, i.e the top spigot is 3" and do not have the lower fins.
I'm looking for the heads with the lower fins and to fit the 3-1/6" spigot.

Thanks
Clive S.


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Bit confusing! as your picture shows post 1960 with the fins underneath. Unless the pic is of ones you need of course.

I thought the lower vertical fins came a few years after 1960.

My info says from 1960 onwards major changes were made. Flat top Pistons, new design cylinder heads etc. I've found many 1960 machines to have the 1959 top end. From 1960 the top spigot was changed to 3-1/16. As luck would have it I've just got off the phone with Steve (AMC Classic Spares) and he's sending the correct ones, as pictured. I did poach this pic from someone else looking for the 1960 heads as well.


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Your info is correct Clive. The vertical fins under the exhaust ports were first featured on the heads for the 1960 sales season, so would have been in production from Sept. 1959 onwards. Compared to the earlier 650cc heads, the exhaust port angles are quite different (so exhaust systems will not interchange), the inlet ports and manifold are different (more off-set and swirl on the '60 type), the combustion chamber shape is shallower and requires matching flat top pistons. Additionally the valve stems (inlet and exhaust) are longer on the '60 heads and the required valve clearances are 0.008" as opposed to 0.006" on the earlier heads etc. Off the top of my head (please excuse the pun) I can't remember if the valve head dias. are the same!
Cheers, Bob.

Cheers bob, Steve Surby and I had a good chat about the differences. After checking the parts lists on Amoc spares the rockers look to be the same and the spindles. The valve springs have different part numbers from the earlier ones so I assume the stems are longer as you suspect. Hoping to save some money using the rockers and spindles off my 1959 heads.


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Yes, the rockers and their spindles didn't change from around 1955 onwards. The valves differ in stem length pre/post '60 and this is why the valve springs and their retainers are different too. The valve spring retainer collets are, I think, the same.
Cheers, Bob.

I have a spare RHS 1960 head available if anyone needs one. Just the one side.
Steve

Funny enough I am rebuilding a 1959 AJS 650 and it has 1960 heads that don't fit the barrel spigots