At the last inspection, the plugs looked black, which the mechanic said was normal for a Rotax that has just landed then taxied a distance to get to his shop. They were new enough, he recommended putting them back in the engine.
Also, it runs fine: it gets the same static RPM it always has, the same cruise speed (110 knots TAS) at the same rpm (5000), starts easily and runs smoothly. When it's throttled up after idling for an hour or more in flight, it's always smooth, so apparently, not enough soot to cause problems.
I was hoping to also hear from a Rotax engineer about this, who might be more definitive about the issue.
