I have a 912 uls that i have been trying to figure it out it fowls the 2 front cylinders when it sits for a few days i have shut the fuel off and run it dry and make sure i purge the oil out of the motor still does it syinked the carbs 50 times new gear box the carbs are new before I got it but previous owner had the same problem that's y they were replaced. I can put new plugs in and fly it and have no issues for about 2 flights 3 flight it will have a 3 to 400 mag drop by turning off the left mag so that means it is on the right mag I would think always the same has soft start module on it. Had annual done all compression is 78 over 80 all 4 cylinders. it is a Rans s7s if that matters had another motor just like this in a same style airframe and never had this issue. the plugs will be black when you pull them upper and lower and it varies from right to left on the front cylinders never the rear ones change the plugs and runs like a top all day for 2 flights no problem. Thanks in advance.
