I tried the Z6 timing belt with this combo and it was too loose so I tried the Z1 timing belt and it fitted on perfect with no problems.. But the problem is that whenever i put the crank and cam to TDC, I try to put the timing belt over the cam but the crank shaft keeps moving and gets out of time.. How can I prevent the crank from moving when sliding the belt over?

 

Have someone hold the crank? There should be enough compression to keep the motor from spinning. Loosen the timing belt tensioner and you should be able to slide the belt on.