outlawmower, you are on the right track for port shape for the Kohler K series. You want a D shape intake port, you might want to first weld/braze up the top above the flange square with the engine deck, even though you shape it into a "D" shape you still want to raise it as far as you can, and when you do and you have not built up this area then you will weaken the flange and break the flange off. The short side radius is the side for the flat, becareful around the head bold hole to the left side of the port, but if you grind through don't worry it is not the end of the world you can fill it with a stud and glue it in. The bottom of the intake port you just want to smooth and blend, knock only the front edge off the valve guide-maintaining the dia on the guide hole all around. When you make your intake manifold you will want to bore the carb. end 1/8" to 3/16" larger than the backside of our carb. then taper to the other end-matching a round diameter that your port would have been before you made the "D" shape then blend it to the port leaving no lips or sharp edges. As far as the dead spot on the Kohler engine you will get that on almost all Kohler carbs running racing gas or pump gas, there is no accelerator pump in the carb, and if you try to tune the idle circuit to run fat trying to get the dead spot out you will only cause the idle circuit to surge with the high speed circuit on top end, the Kohler carbs on gas are only good at idle and top end. I am hoping to get some pics of my stuff in the next few weeks, then I can show you better than explain what I am talking about. Stay with the "D" shaped ports for a Kohler K series. And don't let anybody talk you out of it