I bought an OS max 52 surpass 4-stroke for my .40 size spitfire I am building, I got a good price, 50.00 It has a prop on it,, I turned it over by hand and noticed there was not much compression at all, on the compression stroke,I hear the valvetrain moving, so I believe it is all working,, The seller told me that the engine will not really have compression until it has fuel in it?? is this true,, I am new to these engines, I bought it he seemed like an honest enough old timer,
Thanks fellas

I also have to mount it inverted, I was told I have to use an onboard glow driver to help prevent flooding and dying at low throttle?