Jodi in your post you said that the engine spark doesn't retard until you have a RPM of over 300. I presume this feature is built into the ignition so you can time an engine by moving the prop very slowly since at the very slow prop speed the engine is at full advance?

Correct timing seem to be an issue with CRRC engines. I have two and both were timed with WAY too much advance, 44 degrees, and 40 degrees.