Throttle,
A few more tidbits:
1. Break-in should start with a series of rich two minute runs on a bench. Each run should be followed by complete cool down. This is called heat cycling and enhances the fit between the iron piston and steel cylinder. Every few runs turn the needle a few clicks leaner. If during a run it starts to slow down, stop it, let it cool, then continue a few clicks richer. When it will run at a lean setting without sagging (slowing down), it is broken in. If you break it in properly, it will reward you with many, many hours of use.
2. They run smoother with the low compression head.
Good luck with it.

George