Cylinders are measured in the following way:
I. Before measuring cylinder wear, wipe the cylinder clean and examine it for scores and visible wear.
2. Place the cylinder-bore gauge across the cylinder, just below the unworn ring ridge.
3. Turn the bezel to set the dial gauge to zero.
4. Move the gauge slowly up and down the cylinder to measure taper. The pointer will move on the scale.
5. Turn the cylinder-bore gauge 900 in the cylinder to measure out-of-round.
Out-of-round = difference between A—A and B—B
Taper = difference between A—A measured at the top of the cylinder and A—A measured at the bottom of the cylinder
The top of the cylinder suffers the greatest wear, and this leaves a definite ring ridge in a worn cylinder. The lower ring ridge is not as noticeable because less wear occurs at the bottom of a cylinder. The bottom of the cylinder below the ring travel is almost unworn.
This is a series of parallel lines or low ridges running around the bore. Waviness can be at any part of the bore but is mainly found in the top regions of ring travel. Waviness is a condition that is hard to measure, but it can be seen and can be felt by lightly running the finger vertically in the bore.
This is evident from small areas of the cylinder wall that have discoloration and minute raised areas in which particles of the piston ring have cold-welded themselves to the cylinder walls.
Incorrect type or grade of oil could create problems. High temperatures will break down the lubricating-oil film and allow metal-to-metal contact between the piston rings and the cylinder wall.