This is a perennial difficulty with the steel points assembly if insufficient clearance is given to the blade spring on the opening point. Because on the steel assembly the opening point is the low tension live one, it is critical the spring can't kiss the camring. Whereas with the brass sets of older design, the sprung point was the earth one so if it rubbed, no problem (until rubbed through and broken, which also happens).
If the camring was able to turn, that is troubling. The register pin should locate it, and the cb end cover should hold the camring firmly in the contact breaker end housing of the magneto. If the end cover allows some axial movement, and if the camring is a loose fit, it is possible it could disengage from the locating peg. If that happens, and the camring turns, the internal timing of the magneto wiill be lost, ie the points won't open at the right place in relation to the magnet. A bit of error will not always be noticeable, but more than a few degrees and things will come to a stop. A double whammy if the spring is also touching earth.
The spring blades are equipped with slotted ajustement at the 'tail end' and the blades should be so fitted that they don't kiss anything. If the 6BA screw at the tail is fubarred, then a repair is needed. Nor must they prevent the opening of the moving point. And the camring needs to fit nicely in the housing, and be secured by whatever end cover + gasket or other spacer is necessary to make it so. Often, the gaskets in the recess on screw-on end covers don't actually contact the cam ring . . . so slop is in-built if the camring is a loose fit. Similar issues arise with the other types of end covers.
If it IS a loose fit, the chances are that the spark interval won't be your 180:180 anyway, as K2Fs are notoriously awkward to get spot-on (compared say to BTH magnetos).
Lucas said the steel assemblies, fitted on most later mags, were 'low-inertia'. I'd say they were 'low cost'. I'd also say the spring tension on the moving point is often higher than necessaey, promoting wear on the heel, and noise.
That's my tuppence worth!
Good luck!
Bill
