PSI will depend on the engine and some on elevation. Compression in an engine that is running normally can be from about 120 to 150. Engines can run fairly well down to 100 psi, lower than that, there is usually a notable lack of power and often hard starting. If you have less than 80 psi, it's almost impossible to get 'em to run.
2007 RMK 700, 2008 RMK 600, 1995 AC Prowler 2-up, 1980? AC Cheetah