1/2 Vernier

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.

Valve fully open timing
Timing as of last successful flight122 deg ATDC119 deg BTDC
New timing118 deg ATDC122 deg BTDC


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.

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