A bore gage is required to determine taper amounts & liner roundness. It can also detect a liner that has lost its taper (blown out above the exhaust) because of overheating or excessive wear. The liner on the left (marked B) has almost no taper above the exhaust. Fitting a piston to a liner with this problem is very difficult. Liners with low taper amounts are also prone to piston scuffing if overheated or run at a lean setting; even if the pistons are the high silicon types.
