Hey All,
So today I have had an issue raise its ugly head, and I am hoping maybe someone else can shed some light on this.
Firstly, 912 ULS always seems to run a little rough around the 2500RPM mark, and I put it down to needing a Carb Balance. Other than that, it has always run great, and all is well. This is what happened today...
I did my usual warm up (oil above 50) and then went to do the run up. Had it up to 4000 RPM, and then dropped a Mag like a usually do and noticed an instant and definite miss. Only missed a few times and then went back to normal. It dropped the usual 100rpm, but it got my attention.
I dropped the other mag, same RPM drop, but smooth. No issues.
I then went back to dropping the first mag, and again, it missed a few times. I increased the rpm a little to see if it had an affect and the miss went away. At this point I shut everything down and took the hood off. Checked all the plugs leads were on securely etc etc. Could not see anything obvious.
Jumped back in, and it didn't misbehave. Gave it a good few runups and all was well.
Flew to my destination, and leaving the destination - no issues. Cruised nicely at 9500ft. :)
Returned to my hangar, and I again did a mag drop test, and no issues at all. So I figured at that point it may have been a lead.
UNTIL....
I remembered someone telling me once about rough running at say 2500RPM may not be carb related. So I did an experiment.
At 2500rpm, it's running rough. I drop a mag, and now it's REAL rough (the same one that missed this morning). Drop to the other Mag, and it smooths out a bit! Not great - but smoother. Back to the first Mag and it's rough again. Both Mags, rough, but not that rough.
Above 3000 -4000RPM, all smooth. Both mags drop 100rpm, and I could not replicate the issue from this morning.
2500, they drop RPM, but one mag runs pretty rough, compared to the other. It sort of feels like a vibration rather than a random miss that I had this morning.
Any ideas?
I am thinking to start working methodically - Swapping one plug at a time to see if I can observe it following a plug - If it is a plug? Might not be.
Anyways...
Just FYI - On the cruise, it's smooth as! 5200RPM and no issues that I can sense.
Cheers
John
