My plane just completed an annual, with Paul, so I know it was done right. Carbs did not have to be rebalanced. Plugs showed good symetry left vs. right. Motor ran great with the carb bypass closed. New plugs installed & gapped. Carb floats were weighed and checked OK. (My floats are not in the serial number recall list either.)
Problem is that the motor vibrates while running on left mag only at low RPMs (at idle when shutting down and at say 2,500). Right mag only is fine.
Runup at 4,000 RPM is fine (left, right & both including drop & difference).
The vibration is the exact same vibration feeling that I get when I pull to idle on final.
I'd really like everything to run smoother.
Thoughts?
Low RPM Vibration on Left Mag
Moderator: drseti
- FastEddieB
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Re: Low RPM Vibration on Left Mag
First thing I'd do is install new plugs.
Probably $20 for the plugs.
Many plug problems are hard to track down, so this is a good place to start.
If you want to avoid the $20 expense, you could try switching the plugs top to bottom and see if the problem "migrates".
Easy things first.
Probably $20 for the plugs.
Many plug problems are hard to track down, so this is a good place to start.
If you want to avoid the $20 expense, you could try switching the plugs top to bottom and see if the problem "migrates".
Easy things first.
Re: Low RPM Vibration on Left Mag
New plus were just installed.
Good suggestion though.
A top / bottom switch would be good troubleshooting.
We wanted to pull a few plugs for an additional inspection anyway.
Good suggestion though.
A top / bottom switch would be good troubleshooting.
We wanted to pull a few plugs for an additional inspection anyway.
Re: Low RPM Vibration on Left Mag
Left would be top or bottom on Rotax?
Or does that depen on the manufacturer installation?
Or does that depen on the manufacturer installation?
Re: Low RPM Vibration on Left Mag
Could go either way, depending upon how the "mag switch" was wired. (And of course you know that CDIs are not really mags...)
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
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Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Low RPM Vibration on Left Mag
Based on the definition of a magneto I think you could argue the point about a Rotax ignition.drseti wrote:Could go either way, depending upon how the "mag switch" was wired. (And of course you know that CDIs are not really mags...)
Re: Low RPM Vibration on Left Mag
I have seen new plugs out of the box do this, and I have also seen an idle mixture problem do this as well.
Re: Low RPM Vibration on Left Mag
I also seem to remember someone else saying that to much silicone heat paste will cause problems too.
Re: Low RPM Vibration on Left Mag
In my experience, rough running from a bad plug does not manifest just at a low RPM ignition check, and an idle mixture problem would show up in examining plug coloration (1 and 3 vs. 2 and 4). So, I remain baffled.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Low RPM Vibration on Left Mag
As a general rule if there is a problem that shows up after maintenance it usually has something to do with the work that was done. My guess since it is at a lower RPM and on one mag that it is likely carb (mixture) related.
Re: Low RPM Vibration on Left Mag
Perfectly logical, Tom - except I did nothing that would have changed the mixture! A slight vibration occurred when I did a runup at 3k RPM. Richard had always run up at 4k, so had not seen this before. I ran up at 4 and everything was smooth. So, maybe the problem was there all along, but that power setting had not been explored before? (i'm not opposed to rechecking idle mixture, and maybe even replacing plugs, if he brings the plane back to me.)
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
- FastEddieB
- Posts: 2880
- Joined: Wed Jan 07, 2009 9:33 pm
- Location: Lenoir City, TN/Mineral Bluff, GA
Re: Low RPM Vibration on Left Mag
Wonder why a carb issue would show up on one ignition and not the other?
Re: Low RPM Vibration on Left Mag
Let's say one carb is running too rich. Assume this fouls just one plug (not all that likely, but bear with me). Now we would get an abnormal ignition check. But, that would manifest at any RPM, not just one narrow range - so I don't think that explanation is the right one. Thus, I remain confused.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
- FastEddieB
- Posts: 2880
- Joined: Wed Jan 07, 2009 9:33 pm
- Location: Lenoir City, TN/Mineral Bluff, GA
Re: Low RPM Vibration on Left Mag
Think horses, not zebras!drseti wrote:Let's say one carb is running too rich. Assume this fouls just one plug (not all that likely, but bear with me). Now we would get an abnormal ignition check. But, that would manifest at any RPM, not just one narrow range - so I don't think that explanation is the right one. Thus, I remain confused.
Re: Low RPM Vibration on Left Mag
drseti wrote:Perfectly logical, Tom - except I did nothing that would have changed the mixture! A slight vibration occurred when I did a runup at 3k RPM. Richard had always run up at 4k, so had not seen this before. I ran up at 4 and everything was smooth. So, maybe the problem was there all along, but that power setting had not been explored before? (i'm not opposed to rechecking idle mixture, and maybe even replacing plugs, if he brings the plane back to me.)
As I recall the issue wasn't rough at 3,000... it was that we were not seeing a drop at 3,000 to check mags.
- Richard
Sport Pilot / Ground Instructor
Previous Owner: 2011 SportCruiser
Sport Pilot / Ground Instructor
Previous Owner: 2011 SportCruiser