Hello FN,
Identifying pre-war Villiers motorcycle carburettors like yours is confusing at first but becomes easy with a little study. There are four basic sizes all identified by the diameter of the manifold they clip on to. These are,
Junior and Midget= 7/8",
Light Weight (L/W) are 1",
Middle Weight (M/W) are 1&1/8" and,
Heavy Weight (H/W) 1 & 1/4".
Ignore the H/W. It was only made for a few months as WWII started. It is very rare. I have never seen one. The only ones of any concern to you are the L/W and M/W.
The Mk 3 and patent numbers and suchlike stamped on the float bowl mean nothing. Forget them. They are no help whatsoever.
Many of the parts across the range are interchangeable. This is both good and bad. The incorrect top on your carburettor shows how this.
Luckily most of the parts required on your carb for the best double lever set up are identical to those used on the 6E engine introduced in 1949. These should be available at Villiers Services.
I suggest for good information you buy a copy of "The Villiers Engine" by BE Browning. It has all the basic information on rebuilding an M/W carburettor. It was first published in 1949 and in many editions thereafter. You will find the second or third edition suits you best. I would also buy an illustrated spare parts list for the 6E engine as that will show all the parts required to build up your M/W with a double lever system. The double lever system merely allows you to tune the carburettor from the handlebars while riding. It makes starting and riding much easier.
If you need an further information, just ask.
