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I have a Jabiru 3300 on my Xenos with an Aerocarb. The engine suddenly started running rich. I've had over 400 trouble free hours until the other day it started running rich and would barely idle. Plugs were sooty black. Compressions were good. I could find no blockages. The air cleaner was clean. I could get it to idle smoothly if leaned almost to idle cut off. The needle seemed to be OK although I have not taken the carb apart. The throttle and mixture cables are secure. Has anyone had this problem with the Aerocarb? Or am I barking up the wrong tree and there's something else going on?

Dave
Xenos N29DN

Dave, you mention a clean air filter. Is it a K & N and had you just cleaned and oiled it? It's very easy to use excessive oil which serves to choke the engine. Otherwise, it's more easily explainable to suddenly experience a lean condition rather than a rich condition. Puzzling.

Thinking further.........I wonder if the Aerocarb needle orifice has come loose. I'd open up the Aerocarb and inspect for that possibilty.

Art,,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,,Jab 3300 #261/Aerocarb

It turned out it wasn't running rich, but had "dirty" distributor caps. After a thorough cleaning it ran fine. Now I need to determine how they got dirty.