Originally Posted by Speedpants
apparently it is an issue with the exhaust valve guide oil seal being made of imperfect rubber(basic description). The seal when working correctly will keep engine oil from the head from making its way down to the face of the exhaust valve....but when it expands or comes off its seat it will allow oil to leak by
This may be the cause of what I am seeing. In my case the engine has 600+ hours and in the last 100 hrs the amount that has leaked out isn't enough to drip on the cowl.
The assembly lube in the stud hole theory probable isn't it based on the hours.
I saw on the Rotax forum a possible explanation, an exhaust leak combined with a sinking float washing exhaust soot out. I thoroughly cleaned it and will be watching.
I did check the torque on the nuts and they all in excess of 100 in lb.
The right side of the engine, cylinders #1, #3 run hotter than the left by 50 degrees based on the EGT's. I am not sure if that is a clue.