Some clatter is normal in larger engines. We've heard this on engines of all types .90 and larger. We've never found any evidence of internal damage on these, and have concluded it's an exhaust note, probably caused by imperfect firing at mid- to low-throttle settings.

If the high-speed needle and idle mixture are set correctly, you just have to let the midrange and low-midrange take care of themselves. If you have doubts, increase the idle RPM slightly and richen the idle mixture a hair. This should help richen the midrange a bit.