The cooling of our nitro fuel is much better than normal gasoline.

I have seen many different port types in same model engines and all were arround the same operating temperature. It is just a design but does not say a thing that a different design is working different. It is all about the designer what he thinks is good.

Maybe the heat is not comming from the normal engine but from the pull starter. The shaft comming out of the rear has no bearing but just a bronze bushing, that will create friction heat (and power loss). And because I have seen many things happen during the devellopment of an engine I know friction heat can raise the temperature a lot.

You have to face it, your engine is just a low cost simple RTR engine. It is cheap made with no special materials and what you will change to it, it will never be as good as an engine from the better brands. The design creates an operating temperature which you should not change when the engine is allready used because after the break-in the fit of piston and sleeve is set to that temperature.