In the original design the liner was clamped in the cylinder block by the head and head gasket. This was not a good move even though I thought that the expansion coefficients of aluminium and brass were close enough. This time I fixed the top of the liner in place with Loctite and then faced the block and liner together. I punched another head gasket with the original template and reassembled the engine.
The compression was now good, but it still ran badly
Next step the ignition system. The timing was still correct but the spark seemed rather weak. The supply voltage to the Rcexel ignition was still a steady 6V so I decided to go back to the coil system that I used to first get the engine to run. This was much better, not the best as I will have to adjust the timing to compensate for the Rcexel advance curve.
I will now have to decide to keep the 6V system via a 7806 regulator or rebuild the Vellman ignition back to it's original 12V form with a 12V motor bike coil
I finally took the cover off the Rcexel ignition to see what is inside. Mostly potting compound