Yes, this would be their first series of sportbike motors where FEM/CFD computers were used to give an excellent port design. Unless you wantTo sum up, to us mere mortals, Yamaha has dome a good job with the std port design, and a bit of light cleaning up is all that's required.
the motor to work at only 10,000-12,000 rpm, I would stick with the
original port DESIGN. That's what I did.
The reason I post caps for DESIGN is that the shape in your engine isn't
quite what was designed, because of mass production. There will be
sharp edges, casting roughness, spatter, misalignment (during casting or bolt-up), and grooves from the valve seat machining tools.
I took a dremel-type tool (cheap hardware-store brand though) and
cleaned all that up. It's called PORT-MATCH and POLISH. Google that
and have a read. I didn't polish to a mirror finish, just like Kiwi I
left it with a "brushed, or coarse-sanded" look.
I ended up with a very smooth power curve, and a bigger power boost
than could be expected from just a 4% capacity increase (1040kit at the
same time).
I also polished up the combustion chamber as smooth as possible without
changing the size or shape of it at all. This has helped me run on normal
pump gas with compression boosted to 12.7 and no pinging/knocking.
Not the cheapest crappy gas, wouldn't put that in my mower, but
the middle one.