I would respectfully disagree, though they need to be somewhat rich, pouring raw fuel does nothing.

I've broken in a pile of nitro helicopter engines.

Start out a little rich and it will run richer/cooler as the ring starts to seat. You lean it a little as a time until the motor no longer requires tweaking (3-5 tanks depending on oil content of the fuel), then you let it rip. I'm talking engines without a prop blowing on them running at 16-18K so they are operating in a lot harsher environment as an airplane engine.