After the debacle of the valve sleeve rotating because I had not secured it, I secured it with a grub screw, and had another attempt at running the engine today.
But before that I shortened the valve lever blocks by 2-3mm. I had noticed that air was entering the cylinder well before top and bottom dead centre. Shortening the bars delayed the entry a bit. Still a little bit before TDC and BDC, but watch the videos to see the result.
So, it is still not finished, and the timing will need some fine tuning. But it works! Phew..
It works in forward and reverse, depending on piston position when it starts, or if the flywheel is given a initial swing.
In the above videos the engine is not bolted to the box, and some of the noise is the cranks hitting the box. The valve arm being hit by the striker is also contributing to the noise.
I will work on the gas burner next.