Need Porting Advice

Around the guide isn't really in the path of intake flow, so I wouldn't sweat it too much. On a flathead, the bulk of the intake airflow is across the roof of the port and then across to the piston side of the valve (the valve is badly shrouded on all other sides) Focus on all the sharp edges and any obvious choke points. On the exhaust side the gasses will be mostly on the floor of the port but the same applies. As for raising compression, bear in mind that as you reduce chamber size you also move it away from the piston and increase the already bad valve shrouding. Be cautious that these castings may be a bit thin in places so don't go too nuts. Air cooled engines go through a a lot lore thermal stress than water cooled so epoxy will be risky. Also don't expect miracles a 20% increase in performance, which would be a huge gain with any engine, would take a 5HP engine to 6. That said, these little engines were built to a price (cheaply as possible) and I'm sure there are gains to be had.