Compression test pressure is measured by kicking the bike fast with the throttle open until the reading tops out and stops rising. A good 250 will be around 185 - 200, 300s a bit less, more like 175 - 185. You have to kick fast enough to make normal leakage through the rings and in the case of the 300 the bleed hole not a factor. Compression ratio is the volume of the cylinder from the top of the exhaust port plus the volume of the head divided by the volume of the head. No way 14:1, usually around 7-8:1.
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