This is the valve retaining collar of the type fitted to Douglas 2 3/4hp models, used to retain the valve springs by means of this collar and a steel pin that fitted through a hole at the end of the valve.
The typ shown here has a slightly modified design over the original - having an additional milled slot, to help retain the pin and prevent collar spinning around the valve. The collar is CNC manufactured from EN24T while the pin is from Silver Steel.
Note: I am told that the original design specification for these collars for the Douglas 2 3/4hp was to have just the recess - without the milled slot (we also manufacture that type - Item 0730).
However, when I originally manufactured these collars, I took the design from an original collar which had a similar slot recess. I cannot be sure if this was just wear to an original type collar, or if someone had modified that collar - but from an engineering perspective I feel the additional slot is a better solution as it should ensure the pin is more captive and more importantly stops the collar from spinning around the valve - I have a couple of examples of old valves where there is clearly a wear groove on the top of the valve where this has happened. I am not an expert on this engine in use, hence I offer both types (however, I am building my own project bike with the modified design, and will report back once the engine is running)
This listing is for the original type - consisting of one collar and one silver steel pin (4 required per engine)