First of all I am no pro here. I have however been able to take seized engines and make them run again. you said it turns freely and has good compresion. I would soke it in castor oil and rotate the crank by hand working the castor in as much as possible, then drain it completely. I would then be ready for a test run. Ensure your glow element is not flooded with oil first. It would be a shame to burn out the element.