Mad,

Your engine is definitely not getting enough cooling air in the cowl. Either not enough air is going through, or the ait that does goe through isn't going through the engine's fins.

The main thing to consider is the fact that air entering a cowling must pass THROUGH the fins of the cylinder and head. If you can see the air outlet from the inlet, then it's not going through the fins.

You may have to baffle the engine to make sure that the air going in actually goes through the fins.