It was running ok before on the Dyno without problems.?

Has the Cam Belt been off at all since it was running last and then maybe not timed up correctly, check all the timing marks with dizzy. 1 tooth out will cause problems.

Have you checked the Phase Sensor inside the Dizzy – no corroded wires & check GAP.

Have your just put the engine back in and put the Connector\loom\wires from (CPS) Crank Position Sensor to the dizzy by mistake. – check you have the right connector on Dizzy & CPS.

Check GAP on Phase Sensor in Dizzy and GAP on CPS.

hope that helps mate.
thanks,
Manoj