I drilled a new 8mm bore through the centre of the fly wheel gripping the outside of the flywheel so the hole was concentric and tapped it to hold the flywheel to the crank shaft. Flywheel complete -well nearly, just needs a good polish!.
I also had to made an adapter for the small 24 tooth spur gear so that it could be also held to the crank. The plans call for the spur gear to be attached to the flywheen but I figured I`d have no problems just using grub screws to fasten each to the crank independently.
Here is the con rod and piston.
So it is looking quite good now and turns nicely with a push on the flywheel yet has a great piston seal