The engine looks like the the standard 150cc case but with nicer machined covers and flat black paint job. I'm kind of doubting that the engine is designed for 250cc. Even if it's a 230cc head on a 150 case, it might be a motor waiting to blow up after a while...which was the problems with their 200cc engine. Unfortunately, I don't know anyone in ZongShen but will keep my ears open.

250cc on a bike that small would sure be fun though!

CC