Is there a stamped number on top of the pistons, like STD., 20, 30, 40, etc? If so, that's the oversize the cylinder has been bored to- - - -Standard, .020", etc. That's important to get the right size replacement parts. Also, look at the ring ridge, if any at the top of the cylinder. Since the rings don't come all the way to the top of the cylinder, there will be a short section of unworn cylinder wall above the top ring's travel area. If you've got more than .005" of taper wear it's not a good idea to do a re-ring job without boring the cylinder bigger to get it straight again. The wear usually happens in the first 1 1/2" or so at the top of the cylinder, which means the rings will constantly be changing size to try to maintain contact with the cylinder walls. That usually results in a VERY short-life rebuild- - - -10,000 miles or less before it starts burning oil again!
Check for taper wear this way- - - -take a top ring off a piston, and square it up in the cylinder right at the top of the ring travel. Measure the gap at the ends of the ring by stacking up feeler gauge blades until they're a snug fit in the gap, and add up the thickness you get. Write it down. Now push the ring to the bottom of its travel with a piston to keep it square in the bore, and measure the gap again. Subtract the bottom gap from the top gap, and divide the result by 3. You've got a good approximation of cylinder taper, which should be .005" or less.
Jerry
