With a couple of other projects completed it was time to get back to the ideal.
The cylinder head was turned to form the spigot that locates it in the cylinder, I also tool a light skim off the small boss on the outside to clean it up and that proved useful as a way to hold it for drilling the 7 air hole sone one smaller gas hole as well as the larger reamed hole for the valve. I also took a light cut off the face so the surface was totally true to the valve hole.
The gas entry boss was milled flat, a 1.5mm hole drilled to meet the smaller 0.7mm hole and then opened up and threaded M5x0.5 for a gas fitting.
Jumping back to the liner the flat to allow the cooling water to flow to the lower inlet was milled
Then with the liner resting on that flat the slots for the exhaust were milled
The four M3 holes to hold the head on were drilled and tapped and then the liner was bonded in place with Loctite 648 and set aside for a couple of days to dry right off.
Once dry the head end was milled to final length ensureing a completely step free joint.
I did not take a picture of the piston as it is no more than a cup turned from 25mm cast iron bar with an M4 tapped hole in the end. This hole takes the threaded gudgeon pin carrier which I made from aluminium. I have gone for a ringless piston just running in the lapped cast iron bore.
The original engine has a brass or bronze conrod so a suitable bit was reamed and roughed out
Then taper turned between ctr and boring head after which the big and little ends were milled to shape.
Some simple turning produced the crank pin, valve and gudgeon pin which gave me enough parts for a bit of a play. All seems to go round as it should and the inlet valve is making the right sort of noises.
