Barrel and head

Looking at the barrel I can see its a three port head, on a two port piston and two port engine cases. Will that have an effect?  The exterior of the base is 66.5mm whist the inner diameter is 52.5mm I think.  I need to recheck the sizes as none of the pistons I have fit.

As in the third and fourth pictures show the rear third port that was covered with a bit of a lilt can.  Is there any benefit in widening up the ports in the barrel?


Here is the head, usual four hole still has the spark plug in but may be replaced or not depending on keeping the head and barrel.

The first photo shows all the fins intact, whilst the second shows the internal part and is quite clean and unmarked. The last photo shows that the head is marked with px125 making me think that the head isn't the original one but a px125 one.  This makes me think that the engine may have be converted to 125, to be ridden on a learners licence.