The Boyer comes with two different rotor fixing bolts

The problem here is that both the end of the camshaft and the rotor have the same thread - so the rotor won't tighten up properly onto the taper (and also makes it difficult set the timing)

The solution is to grind away the first 6.5mm of thread of the retaining bolt to clear the thread in the rotor so it can be tightened up properly onto the taper

Cut the bolt to 15mm

The thread in the rotor is retained so you can still use a puller to get it off the camshaft