have the maximat7  in my hands (well in my work shop) lots of cleaning, 2 gallons of evaporust on hand, All will get a good going through...   will need to find some base material for it..

Fantastic Andrew - you have made great progress, I look forward to following this interesting build 

This is my own design which I have been building for the last few months. It is a bit of scrap box special, hence the cylinders made from 22mm copper pipe. The crankshaft runs on skateboard 8mm ball races and has a centre plain bearing.
I am planning a single rotary valve driven at half speed by a timing belt, going to mock it first before  cutting metal to make sure of the concept. One concern is that there will be too much friction from the shaft and belt drive for the engine to overcome, we shall see.

Andrew

Square holes???? Are they really necessary? Seems like a lot of faff for what return? I've looked at Jo's build (see last pic) and it appears she thought the same .............

Maybe a hole which is 3/32" or 8BA clear will be suitable?

EDIT: actually looks bigger maybe 5BA?

Set the flywheel to run as best as possible to the inside edge of the rim as you won't be turning that. This applies to a chuck as well as a faceplate.

When you flip the flywheel over you don't really need it perfectly concentric as you are only making facing cuts. If you do need to clock it in then a dti on the machined face and a few gentle taps will do it if you just nip up the clamping screws.

As for polishing the rim, I would think this engine originally ran a separate belt pully so the flywheel would have been completely painted