No theoretical objection. You'll just have to find the space for it.
Creating reasonable directions will be based on some good stuff I read somewhere about Pizza slices, or something.
Airflow won't be the problem; heat flow from the cylinder bore to the outer ends of the cooling fins will be, and there is not a great deal you can do about that.Cooling the lump shouldn't be my biggest problem, Lots of airflow available.
Cast-iron will be cast-iron, you know.
Now we are running into conflicting desires. With maximum power at 9500 rpm, you not only need over 100 mm of total transfer port width, you'll also need a corresponding amount of blowdown angle.area. With 190° exhaust timing that just isn't achievable. We're dealing with a short-stroke engine here, remember?20HP at the rear wheel will be ideal
You'll need a main exhaust port 194° high and 45 mm wide and two auxiliary ports, each 192° high and 20 mm wide. And I bet there isn't enough cast-iron around
and the cylinder studs would be in the way. But if you manage to realize the above, and if you don't totally mess things up, you'll have more than 30 hp at the wheel.
If you're serious about the 20 hp, why don't you drop the 9500 rpm to maybe 7000 rpm? Then you can use milder port timings and get a more forgiving engine character.
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