The tapers must be matched !----The nut must be properly torked.--------You start by removing the key.------Then smear a little bit of fine valve grinding compound on the tapers.----You spin the flywheel back and forth / round and round to lap the tapers together.-----Remove all traces of compound.-------Clean the tapers.-----Install a factory key per the manual.----Torque the nut.----The key will not shear again !!!!