Early S1 engine case

[steveg]

I've got an engine which I believe to be from a S1 frame breather but the number suggests it's much later (S3).
Is there a way tell the difference?

[vegansydney]

Is the drive side bearing housing beveled for an oil throw washer or not?

[steveg]

I've not opened it up, I was hoping there was a tell on the outer.
It has the smaller exhaust studs, do you what year they changed?

[vegansydney]

The exhaust studs changed during S2 production (November 1960) from M6 to M8.

[steveg]

So that definitely rules it out as S3.
I have found a reference on the BLA page that states some of the S1 engines started with 7, so think that will do for me.
Thanks

[vegansydney]

The Series 1 LI 150 engine case starts with a 7, as does the 150 Special.

[steveg]

The Series 1 LI 150 engine case starts with a 7, as does the 150 Special.

Do you have a source for that?
As a lot suggest S1 Li engines start with 5.

[vegansydney]

The LI 125 S1 engine starts with a 5, but the 150 S1 starts with a 7. I know this from owning a Series 1, but it is well documented in several of Vittorio's books, the Spanners Manual and on several websites, such as this one.

[steveg]

The LI 125 S1 engine starts with a 5, but the 150 S1 starts with a 7. I know this from owning a Series 1, but it is well documented in several of Vittorio's books, the Spanners Manual and on several websites, such as this one.

Thanks for your help, it's resolved now