I've been running the iridium plugs now for a few hours. When I installed them I gapped them to Jabiru's recommended setting .021". Now that summer is gone and Victoria is pretty cold I've been finding that it hasn't been starting as well as expected, needing choke longer etc. Also in cruise there has been a bit of barely perceptible hesitation.
Anyway, on the weekend I was talking with a knowledgeable mate from West Sale who said, "Did you re-gap the plugs?" And if so, "Don't. Just leave them as they are set by NGK." That's about 0.028".
This morning I re-gapped the iridiums to 0.028" and lo and behold, it started much more energetically with little need for choke. Also in cruise it has never been smoother nor more even.
So the moral of this story, leave the iridium plugs gap alone as they are set by NGK - they know what they're doing.