Pinasco 215 not designed for Long Stroke...

I worked out one reason for the power loss, it appears that although it fits fine without a base gasket (but with a bit of combustion chamber adjustment to correct the compression), the Pinasco 215 kit is not designed for long stroke.

After pulling the engine apart I have found that the piston top has flattened out. This is a sign that the piston-to-spark clearance is too small (i.e. the top of the piston is heating up too much). By measuring various bits I have found that the cylinder of the Pinasco sits ~0.5mm shorter than standard. More worrying is that the difference in spark plug depth in the head is 2mm. If the kit was designed for a 1.5mm higher piston, then I would not expect the cylinder and head to put the spark 2.5mm lower and some info I found in German seems to tell the story correctly

So I have damaged my kit a bit and will see if it can be saved or need replacing. The trick seems to be to use a standard head and adjust it for the Pinasco i.e. for standard stroke use Pinasco head (or Worb5 adjusted head), for long stroke either use base gasket or adjust a standard head (where the spark is 2mm higher).

Note: the true measurements for the above can only be done with the piston in place, since the Pinasco piston and standard piston are different (however I doubt very much that they would be as much as 2.5mm different).