Excessive Mag drop during Runup
in 912 / 914 Technical Questions
11 years ago
My Titan Tornado II powered by a Rotax 912S did not run for 2 - 3 weeks while I replaced a windshield in January 2013. During the replacement very cold weather set into the Northern Utah area (temps don into the teens F.).
After replacement of the windshield, and upon running the engine I noted a mag drop of about 350 RPM when swithcing from "Both" to the "Left Mag" (the condition did not exist prior to the down time and cold temps). The "Right Mag" yields about a 150 to 200 RPM drop. I should mention at this point that aircraft and engine are hangared at a temperature of 45 -50 deg. F., and were not exposed to the really cold temps until pulled out of the hangar for runup and flight.
Could the cold temps be a factor? Nothing else that I am aware of has changed.
I installed new spark plugs to see if that was the problem, and experienced the same mag drops on runup. The new plugs are gapped to .028 inches. Is that too wide of a gap for the colder temperatures? What should they be gapped to for the conditions?
I also ordered a new Spark Plug Cap to compare cap engagement with the "old," as during installation of the new plugs I noted via feel that cap engagement was not equal on all spark plugs. As I checked the new cap with one sample plug--one where plug cap engagement felt looser than the rest, I found the new cap to engage more positively than the old.
If re-gapping dosen't solve the mag drop problem, I thought that my next step would be to replace the spark plug caps (not cheap).
Is there a more logical course of action to resolve the excessive mag check RPM drop? Or a better way to diagnose the problem?
Thanks,
Ron
After replacement of the windshield, and upon running the engine I noted a mag drop of about 350 RPM when swithcing from "Both" to the "Left Mag" (the condition did not exist prior to the down time and cold temps). The "Right Mag" yields about a 150 to 200 RPM drop. I should mention at this point that aircraft and engine are hangared at a temperature of 45 -50 deg. F., and were not exposed to the really cold temps until pulled out of the hangar for runup and flight.
Could the cold temps be a factor? Nothing else that I am aware of has changed.
I installed new spark plugs to see if that was the problem, and experienced the same mag drops on runup. The new plugs are gapped to .028 inches. Is that too wide of a gap for the colder temperatures? What should they be gapped to for the conditions?
I also ordered a new Spark Plug Cap to compare cap engagement with the "old," as during installation of the new plugs I noted via feel that cap engagement was not equal on all spark plugs. As I checked the new cap with one sample plug--one where plug cap engagement felt looser than the rest, I found the new cap to engage more positively than the old.
If re-gapping dosen't solve the mag drop problem, I thought that my next step would be to replace the spark plug caps (not cheap).
Is there a more logical course of action to resolve the excessive mag check RPM drop? Or a better way to diagnose the problem?
Thanks,
Ron
