Duff rotor arm, another chocolate part

[cleverusername]

Been having problems with my Sprint conversion, the engine misfired when reved above 3000 and then stopping starting completely. I was worried because this is an engine I rebuilt and I thought I had done something very wrong or misjudged the amount wear.

In the end the problem turned out to be one of those black rotor arms with the rivet in it (I am using an Ambassador cap). I had used one on the 1500 with no problems but after being able to find no other issues, I replaced the black rotor arm with a much more expensive red one.

Instantly fixed the problem, fires virtually first time, requires much less choke to keep going and revs all the way to 5000 without a hint of a misfire (haven't dared rev it any harder on the drive). Complete transformation, yet I can see nothing wrong with the black cap. No crack, signs of burnt electrodes or other shorting. It is amazing how much difference changing one little part can make.