I had a very satisfactory day in the workshop, yesterday. Worked on another mod, to try to improve balance.
The displacer has a balance weight....... But the relatively heavy piston hasn't...... It wags the table from 200 rpm!

I made a quadrant from 1/4" thick brass. Then drilled & tapped the side of the bob weight 4BA......

Screwed it into place......

And turned it down to crank throw diameter......

Now it looks like this. Balancing the piston.......

Started up. Much smoother, straight away.

Happy top revs now, are 450 to 500.
Any more than
this, it starts to jump around....... Again!

It's
never gone over 400 rpm before........ This time it went up to 578rpm!
Almost 50% extra revs, just for improving the balance!

David D