I removed the old, rusted plug and put a new one in. I fueled it up, opened her up about 2 times, primed and went at it. She did not want to fire, however, despite good compression. At the time it was about 30 degrees out, and it took some time to get my other engine going, too. What should I do? Thanks!

Are you sure it was rust on the plug? IF it got that bad your engine needs to at the very least be opened up and cleaned.

reset the the needles to factory (that includes the low end) if you have an electric starter use it and make sure your glow is charged...

Steven

Thanks. I got it going. Just needed a wet start. Thing is a power house, and the muffler is huge!

If the plug was rusty I'd want to disassamble the engine and clean it well.

The thing is, once I take it apart, I know it's not going to go backtogether and function.

Sure it will
Really though if you lay the parts out on some clean paper towel and visually inspect each one clean anything that looks suspicious.
The bearings and crank are susceptible to rust. the rust from these will do NASTINESS to the cylinder and ring or piston if ABC.
It is well worth the effort to clean it well.
Although the engineering of a good RC engine is complex the parts assembly is simple. If I can do an overhaul ANYONE can
A new O ring on the needle valve never hurt either.

Okay, so how do I go about doing this? Simply take it apart? What parts need to be oiled etc?

Just take off the backplate. You don't need to remove the head..becuae there's an opening from the exhuast port.
Unless you still want it to be purple

Remove all plastic parts....O -ring of the carb's throat, needle valves (HS and LS.)
Or don't even mess with the carb(soak it)...but remove it from the engine.

Let the engine soak in fuel over night...all the parts

The only reason I would take it completely apart is becuase the out board bearing.

That's only 6 more screws on the head.lol

Becareful with the head's shim. After removing the head.
Slide out the cylinder sleeving..notice a little notch...it's fool proof.
Or the exhaust port gose on the exhuast side.lol

Slide the piston's rod from the crack and remove the pistion/rod assembly from the engine (leave this as one assembly)
Slide out the crankshaft