Villiers MK12, MK12/2 & C12

Probably a stupid question, but what are the differences between Villiers MK12, MK12/2 & C12 engines?

Having looked at the workshop manual I see that the MK12/1 & MK12/2 have a different block casting to the MK12. This looks the same as the C12 on my Warsop pump. Does the 'C' just mean a later Norton-Villiers engine?

mattblack wrote:Probably a stupid question, but what are the differences between Villiers MK12, MK12/2 & C12 engines?

According to Jack Sizer

Mk12 introduced about 1942, Bore 55 stroke 50

Mk12/1 introduced about 1959, Bore 55 stroke 55, (quoted stroke probably a typo in the original document)
Available with various reduction gearboxes (RG) and also in a higher speed version (HS)
Mk12/2 - a slightly later variant, also with RG and HS versions.

412H introduced 1964, no details. Sizer does not mention it.
However, there are plenty of references to a 412H on the internet, these selling under both the Villiers and JAP names (they amalgamated in 1964).

C12 introduced about 1974, Bore 55 stroke 50.
Norton Villiers was formed in the 1960s and so predates the introduction of the C12, however, C12 engines were sold uunder the Norton-Villiers name.

Of course some castings were changed during the long production period, as were other things like cowl design and carburettors.