Mr Cox

I think they were just made in many different versions, perhaps cutting some corners near the end of production with the stock needle valves and running out of non-slit cylinders etc. It certainly looks like the genuine product to me. I only have one of these myself, show below, which I got directly from Ron at the time.

As for running it, you'll have to be careful to avoid wear around the disc. One can easily get galling in that area as there is no Brass or Bronze anywhere. The disc is aluminium, running against the aluminium backplate if I remember correctly.

The location of the pin that rotates the disc is another weak part, as there is very little material for the pin it self. The crank is simply a stock crank while the conrod has been thinned down at the big end to expose a little bit of the crank pin. This gives a rather short pin that sticks into the aluminium disc (less than half of the disc thickness).

I bought mine with the intention of putting an RC carb on it, and using it. But once I saw the construction I came to the conclusion that it is a pretty engine to look at, made for the occasional bench run, but not more.