The 1985 Aero 50 states 114 to 171 PSI is acceptable. This motor has a 6.8 to 1 compression ratio.
The Aero 80 says 142 to 200 PSI is normal and this engine has a 6.8 to 1 compression ratio too. (FYI, I have one engine that starts and runs fine at 90 PSI).
The Aero 125 manual says 171 PSI is minimum and this engine only has a 6.7 to 1 ratio.
As you can see it is not possible to state a number that applies to all 2 strokes or 4 strokes for that matter. That's why there are such things as service manual. Never ever believe anyone who just pull a number out of his * because he heard this or that.
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