[KDS4444]

Hey, all! Am the owner of a 2002 Yamaha Zuma 50cc scooter. It has a new cylinder & head, + gaskets, new piston and rings, and new reed valve gasket. The engine is not turning over at the moment, and am not sure why. Spark plug is clean and is generating a nice spark. I have a compression tester that says I am only getting around 75 psi when I kickstart it, which I know is much too low. I recently hooked up an air compressor to the spark plug hole, and turned it on. I found no air escaping around any of my new gaskets or parts, but I could hear air whistling out of my carburetor. Piston is at TDC for this test. I know a leakdown test is the standard approach, but I do not have the tester for this— am hoping to figure out where my problem is with my air compressor and some careful listening. The compressor itself is able to get up to about 75 psi when I turn it on hooked up (it goes much higher than this, but only gets up to 75 psi on my engine) which corroborates what the first compression test told me.

Should I be getting air coming out my carburetor when I pressurize the cylinder? I understand that the reed valve won't close entirely without full pressure in the cylinder, so I expect some air to becoming past it, but the carb too? Thoughts? The carb was rebuilt about 4 years ago and has been working fine ever since.