Doing the timing belt on a mates 2001 Focus 1.6 as a favour - now the fcuking thing has me stumped.....No key on the bottom pulley or cam sprocket, there are held in place by torquing up the pully bolt and squeezing them on a slight taper.

The first time I attempted this I just jammed the bottom pully so it wouldn't turn and torqued up the bolt, when I tried to start the engine however I discovered the crank was turning but the bottom sprocket was slipping and the cams were not rotating....

The haynes manual once again has a stupidly vague solution to this "use a suitable lennght of treaded bar inserted into the crank and a nut to torque them up and force the sprocket onto the taper" the idea then being that you then remove the nut and treaded bar and then torque up the new pulley bolt. Thats wonderful except the treaded bar is a standard M12 size but has a finer tread than normal so no lenghts of treaded bar I have will screw into the crank
This leaves me with the option of using the old pulley bolt to do the job but if I torque it up surly when I remove it again to use the new one the tension will just come off the sprocket again?