Take off the dizzy cap, and loosen the dizzy bolts

On the dizzy edge of the dizzy is a very small slit/ timing mark, line this with the centre of the metal strip on the rotar arm and tighten everything up and fit cap on


BUT I bet money when you fitted the head and timed it up the belt was spot on and if you align the timing marks now its a tooth out on the bottom pulley, seen it a million times and brought countless rs's cheap because of it

Don't panic if it is it's just fitted wrong