I agree. I also learned in a shop full of old worn machinery. I call my method sneaking up on the final dimensions. Measure cut measure cut until you are close and then go for it with fingers crossed.
My understanding is the engines with an even number of cylinders are rotary engines. A different animal where the crank is fixed and the cylinders rotate with the prop.
My two cents is either something is mechanically wrong like reversed intake and exhaust valve timing or the head isn't sealing to the cylinder as Jasonb suggests. The finish is rough and before making changes based on a guess you might try smoothing it a bit.
If the picture you just posted is where your sparkplug is now I'd be very surprised if .100 deeper makes any difference. In my younger days I had an old car that burned oil and it had what were called nonfoulers on the plugs. These were spacers which moved the plugs 3/8" or so out of the...
I flipped the segment because if I indexed it any further than the center tooth the top would hit the arbor holding the cutter.
I carefully machined the blanks on locating pins so that they just fit the cam ring. See picture.
There was no problem with deflection.
The money part was the...
I am working my way through building an Edwards 5 cylinder radial engine and I thought I'd share how I made the ring gear that drives the cam. I couldn't bring myself to spend the 200 plus dollars for the Boston gear specified in the plans. I machined three 120 degree segments and was able to...
The two main reasons I find for Allen wrench failure are cheap screws with oversized hexes and dirt or chips in the hex preventing the wrench from fully engaging the hex and spinning.