Do cylinders have to be inspected and/or forcibly reconditioned as part of a bottom overhaul? I know it's sensible and customary because of the practicality involved in having the engine cracked open , but is it required by the reg? And yes, I'm aware bottom OH is the only legal kind of "overhaul", as top overhaul is a non-term...
Bottom overhaul is also a "non term". Engine overhaul must be done in accordance with the manufacturers overhaul manual which requires cylinders be overhauled or new. Charlie Melot Zephyr Engines
That's not what the FAR's say.
43.2 Records of overhaul and rebuilding.
(a) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being overhauled unless—
(1) Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and
(2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under part 21 of this chapter.
It is legal to disassemble, clean and inspect, and put it back together test it and call it overhauled, That's legal, but not very smart.