Forget what I said about the vernier running at 1/6 of the crank shaft. It’s the CAM drum that’s running at 1/6 of the crank shaft.
The vernier for adjusting the CAM timing is running at 1/2 of the crank shaft!
This means that when the 4 bolts are out and moving the prop one revolution as I described here, is not changing anything, as the number of holes in the vernier is a multiple of 2. So every vernier step of 4.5 deg is all you get, no steps in between by turning the prop one revolution.
Now this makes sense, as I have just adjusted the timing, by about 4 degrees, so that’s good.
Next time when I am back I will start assembling the back of the engine again, and see what difference it had made.
Plus will try different fuels as well. Now running 100 octane, but I will try and see what happens with 95 and 91 octane.