Hi Spyke,
Remove the A/R unit completely and clean both tapers with some thinners,
Set the mag and pistons ase you are doing it, assemble up theA/R unit and almost tighten the nut with your fingers, check the mag and pistons again, fit a socket or tube spanner over the A/R nut and give the A/R unit a tap inwards, this should lock it onto the taper, then tighten the nut
Oil has probably gotton onto the tapers since you first did the timing
Have you tried the fresh petrol???
HTH
John