AJS & Matchless Owners Club

Hi

For the 1960 season, combustion chambers were reworked for G80, G80CS and 500/650 twins. For 1964, the G80CS cylinder head was reworked again (026702 -> 031623).
I have seen pictures of the later one - there are some changes to the casting in the spark plug area - but what are the finer points? The late number indicates this was a modification made for the G85CS works machines at first.
Was the firing slot finally abandoned and a 10mm plug fitted?

Cheers,
Knut

Hi Knut,
Here are pictures of a 58CS and 64CS heads. I have two other heads similar to the 64CS, one off a 1968 G80CS and one off a G85. They all use 14mm plugs.

regards
Bjørn

'64 and later had 1 3/8 inlet port standard and inlet valve has 5/16 stem also

Marty, you made any progress with the CS issues you were having?

Different Marty. You are after the Australian, not the Kiwi. As an aside, I attended the Oz Jampot at Boonah, Qld. Met Marty and his problem children. I think he is very close to having both sorted, or as close as one can.

Marty wrote:Different Marty. You are after the Australian, not the Kiwi. As an aside, I attended the Oz Jampot at Boonah, Qld. Met Marty and his problem children. I think he is very close to having both sorted, or as close as one can.

Of course it is, sorry I should have realised by the way you're still beating that bloody animal!!!!

Still it's nice to hear that progress has been made.

I came across this cylinder head in an auction. It appears to be a 1959 type head, p/n 025417. The chamgfered squisch band is still shown, but the ignition plug hole has shafted from the central to an off-center location. This head should only be used along with the 1956-59 piston.
Thus, this head paved the way for the 1960 type head shown above.
025417 was specified for the 1959 G80TCS as well. Despite the larger bore of the TCS, the head works for the bigger engine due to the chamfered edge.

-Knut

If the head you are referring to is the one posted on 21 July in Pictures... then that head is from an early 56 CS short stroke before the centre plug was introduced.

Thank you Jarret. I had no knowledge there were two versions of the 1956 shortstroke head. Do you know the part number? The 1956CS head had #022302, which was altered in 1957 into #023532. Then no change for 1958, and it changed again for 1959 into #025417. These numbers are for heads w/valve guides.
So, apart from the plug position (hole vs. slot), how do you mark a difference between these heads? The later heads appear to show differences in the valve size and valve guides.
Is the head I have shown actually #022302, and the slot firing plug version equal to #023532? No other numbers are found.

-Knut

just as a matter of interest, what was the purpose of the 'firing slot'?
kind regards