classic motorcycle forum

Thanks all clear.

Any tips on an address to buy new centre pieces?
In Europe they seems to be not available.

True enough. Both books and  even better still,  find on-line forums for more real world 70 years on solutions.

Far better, in my experience, is the little Pitmans manuals for most makes, in this case written by the AMC service manager FW Neill.
Usually these books are on Ebay for a tenner at most.

I have never seen any information on the internals of the Villiers centrepiece published anywhere….ever. Further to that, as the centrepiece is made in two parts and very tightly assembled, they went to great pains to tell people NOT to disassemble them so as to look at the internals. There is nothing to gain from doing so and every chance of creating problems for yourself if you do.

Over a long period the top hole of the centrepiece may be worn out of true by the working action of the taper needle. Slight wear may be compensated for by a change of needle but for the effort and time wasted to do this and get it right it is far easier to just simply fit a new centrepiece and be done with it.

Villiers may have altered the internal arrangements of the centrepiece several times over its lifetime. We don’t know, we have no way of finding out and does it really matter? Regardless of the internal arrangements the MW carb on your Mk XIIC still runs best with a number 2 centrepiece. That is all we need to know for successful operation.

The Mk II designation on the underside of the float bowl refers to general improvements across the whole Villiers carburettor range. It serves no other purpose and has no role in identifying any individual part or individual carburettor. Ignore it.

Your 1 1/8" carburettor is a Villiers MW (Medium Weight). It is intended for use with a Villiers lever throttle NOT a later self closing twistgrip throttle.

The Mk XIIC was fitted with the MW (Medium Weight) carburettor as standard. It was set up with a number 2 jet (the centrepiece) and a number 4 taper needle. Both the jet (centrepiece) and taper needle are stamped with the relevant numbers. Be aware it is very easy for the MW needle and centrepiece to be confused with the similar but shorter parts used in the Villiers LW (Light Weight) carburettor. It is easy to confuse the two.

If all parts are in good condition with the float level set to Villiers specifications the carburettor will work exactly as the maker intended without any further adjustment. Please note there is often a difference between what the maker intended and what a current owner thinks it should do.