Can a 4stroke be heat soaked like a 2stroke to break it in ? ,or is it a waste of time on 4strokes .

Works the same on any engine.

Can you explain HEAT SOAKING ???

Heat soaking-repeatedly warming up the engine slowly then allowing it to cool. The heating and cooling cycles allow the metal to 'normalize' which basically means settle into a set shape. When the pistons, cylinders, etc are new they can easily deform until the metal normalizes and the internal stress is relieved. I think Kevin Cameron found this out by trying to modify pistons by welding on the top of them. He welded new pistons and found they deformed badly. When he tried to weld a used (normalized) piston, it retained it's shape. The same idea applies to the entire engine. Many race car drivers try to find 'seasoned' blocks. The seasoned blocks have been heated and cooled many times and will not shift any more, so any machine work will maintain its size and 'trueness' better.