Spark Plug Diagnosis Please
in 912 / 914 Technical Questions
10 years ago
I need some help understanding what these spark plugs are telling me about my 912ULS at 128 hours. I have it on RANS Coyote 2 using the standard Rotax radiator and a oil cooler about 5 by 7 inches, in a tractor configuration fully cowled. It has always run "cool". CHT is usually 160*F and the oil temperature typically shows from 170*F to 200*F depending on the day and RPM. 205*F at 5200RPM and closer to 170* at 4800RPM. I run 91 octane Mogas no alky. I do NOT have an EGT gauge. Plugs were gapped at .026". Field elevation is 1200' and I fly mostly at 3000'-4000' MSL
The plugs show little (if any) difference between top and bottom. The pictures attached show the top plugs at the upper level and the lower plugs towards the bottom of the pictures. Cylinders 1 thru 4 read left to right.
Cylinder #3 shows an almost "perfect" tan color correct mixture? While cylinders #1 and 4 show a sooty rich condition? Cylinder #2 shows somewhere in between? There has been no prolonged idle except for a minute or 2 to back taxi, etc.
I'm stumped as to what exactly to adjust for BEST operating condition. I'm guessing that an EGT gauge would tell all if fitted to each cylinder? Would moving the carb needle to the next lower (leaner) position help? Would blocking off SOME of the oil and water radiators be the "right" thing to do?
I'm not afraid to spend some time working this out. I can take more pictures if needed.
Thank you all in advance.
The plugs show little (if any) difference between top and bottom. The pictures attached show the top plugs at the upper level and the lower plugs towards the bottom of the pictures. Cylinders 1 thru 4 read left to right.
Cylinder #3 shows an almost "perfect" tan color correct mixture? While cylinders #1 and 4 show a sooty rich condition? Cylinder #2 shows somewhere in between? There has been no prolonged idle except for a minute or 2 to back taxi, etc.
I'm stumped as to what exactly to adjust for BEST operating condition. I'm guessing that an EGT gauge would tell all if fitted to each cylinder? Would moving the carb needle to the next lower (leaner) position help? Would blocking off SOME of the oil and water radiators be the "right" thing to do?
I'm not afraid to spend some time working this out. I can take more pictures if needed.
Thank you all in advance.
20150226_082557sm.jpg (You do not have access to download this file.)
20150226_082617sm.jpg (You do not have access to download this file.)
20150226_082632sm.jpg (You do not have access to download this file.)
20150226_082639sm.jpg (You do not have access to download this file.)
