can anyone tell me whether this is a true cooper s motor?
numbers are 9FSAY46895

I'm afraid not











(The numbers are Cooper S, yes. But number stamping is EASY PEASY)

so therefore its just a 1275?

No no... the numbers are Cooper S... what I am saying that it may just be a 'normal' 1275, but with Cooper S numbers.

Chuck some pics up... esp a rear shot of the engine if you can.
We'll be able to tell you very quickly.

without seeing it I dont think antone can really tell you, we could start the 20 questions like does the engine have tappet chest covers or is it a solid type without, if you can get a picture some one will tell you

Jon

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Roundies and Clubbies(except vans) are both ugly that is why I have Midas and a van
1293 Mini Midas Bronze,1275 Clubman van

The number is a Cooper S (probably early 68 )
I would want to see more evidence before I would say what the number is attached to.

Number indicates a 1275 Mk1 Cooper 'S' and if you have the body to go with it, the body prefix should be YKG2S2. Should be real easy to identify or as said before, post a pic and you will soon get an answer.

Am i correct in thinking that all S motors, Mk 1 or Mk2 are differentiated in one of a few ways:

1) Tappet chest covers <--- the biggest giveaway
2) is a 1275 and not a small bore
3) has a number like 9FSAY or 9FXEY
4) come with factory main cap studs and not bolts
5) have factory fitted S ball bearing oil pressure relief valves
6) are accompanied by extremely high price tags

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Lillee - 1969 Morris Mini K

Are you sure about the "have factory fitted S ball bearing oil pressure relief valves"?

That one is UK derived BS I reckon, never seen one factory fitted, in Oz anyway. And I've owned a few S motors....
Having said that all my motors now have them, they give better idle pressure and don't jam with debris.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.