I've just finished building the James Coombes engine. I used the Stuart Models plans, but machined it from bar stock. This is my first attempt at a steam engine. and I don't fully understand how the cylinder works. There are two 3/32x3/8 ports that go to the top and bottom of the cylinder. There is a port 3/16x3/8 for the exhaust. How does the exhaust evacuate the cylinder? I've assembled the engine and have everything moving smoothly with no drag. When I set it up and put air to it,all I get is air coming out of the exhaust. Am i supposed to drill a 3/16 hole from the exhaust port into the cylinder? Thanks in advance for any light you can shed.