Compression test

Normal 8.5–10.0 bar. Wet test discriminates rings vs valves. These are diagnostic ranges, not pass/fail limits — a compression figure is only comparable when the engine is at operating temperature, the throttle is held wide open, both plugs are out, the battery will spin it at full cranking speed for 4–6 kicks of the gauge, and the same gauge is used on both cylinders. Altitude lowers every reading. The difference between the two cylinders tells you more than either number: more than about 10% apart is the finding, even if both are “good”.