A big thank you to all you guys who have taken such trouble to answer my query about the Mills 1.3 shaft thread. Yes, Simon is right. It is 2BA. What foxed me was that I could not screw a 2BA full nut on to the threaded portion of the crankshaft and yet I could wind a 2BA screw in to the prop. nut. On close inspection I see that the end of the crankshaft thread has a slight distortion which is sufficient to stop the 2BA nut and the spinner nut from engaging to start turning. I shall have to get a 2BA die and run it over the threads to true them up.
Regarding the RC throttle I note what brokenenglish says and he is correct. The interesting thing about the throttle barrel is that as it turns the air hole decreases in size restricting the airflow but at the point where it closes completely a tiny breather hole is exposed sufficient to keep the engine ticking over. There is a similar arrangement on PAW diesels where the breather hole is drilled through the carb. body and keeps the engine running when the throttle is fully closed. Personally I prefer to blank it off so that if I hit the throttle cut button on the transmitter the engine stops.
Simon, if you have not yet put your Mills back in the roof can you have a look at the crankcase backplate and tell me if it is inscribed "Mills Bros." Mine is not and yet my Mills .75 is. I always understood that it was one way of distinguishing a genuine Mills from a copy or replica.
Once again thanks to one and all.