I want a motor like this.

First you would need to work out a bore/stroke/ rod ratio that would allow you to got to the RPMs you want safely. Then convert that number into cubic inches per cylinder and that will tell you how many cylinders you will need to get to 400Ci . I have seen the early Kawasaki 750 cc triple 2 stroke motors joined together to make a 6 cylinder engine. That's cases welded together and cranks joined.