Ok I assume this e50 has the same starter clutch deal as on my puch e50 magnum. Pull the spark plug and pedal with the starter cable engaged. See if ya hear the motor spinning. Otherwise that squish is the cam trying to engage but actuall not with success... That's my guess. There should be a way to tighten the cable as a first fix attempt. The compression is probably a red herring. This is rain related and if ya have spark you do have to look elsewhere.