It looks like an older model nova based engine. NovaMega RB Nova Rex, in essence it's all the same. The components are the same.
If the crank is 11mm it's definately an enginedesign of more than 2 years ago. In 2003 we already had the 11.5mm crancshafts.
The carb looks like a model from the cheaper end of the line as it has no changable venturi. But the crank has some work to it. Seems the Novarossi version mixed the lower end carb with the higher end crank.