After you start it, close the needle until the engine is running as fast as it
will go. Then open the needle until the engine just begins to slow down a bit.
You will hear it. That type of engine is much tighter when new, and will get
quite hot, until you get some runs on it. Only run it for a few minutes at a time
then let it cool off. If you had a tach, you could richen (slow down) the engine
about 3-400 rpms, and it would be plenty rich enough to not overheat.

Dave.