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Magneto Timing Help

blueflyer

Well Known Member
I am trying to put my mags back on after a 500 our inspection on a Lycoming 0-360. My mags say left rotation and 25*. When I test run, the right mag is not working properly. Here was my install method:

1. I internally timed the mags with the timing pin in "Left" hole until it dropped onto the shoulder on the pin.
2. rotated prop to get compression on cylinder 1, then clocked the prop to put it at the 25* mark on my flywheel/starter marker
3. Installed the mag on the engine with the pin inserted, then removed the pin.
4. twisted the mag to where the buzz box would just turn on, then move back so it would just stop buzzing
5. Then I externally timed the mags to the engine using normal methods. The buzz box (left and right) lights up dead on at the 25* mark. Makes me think they are timed really closely.

I removed the right mag and rechecked the internal timing, but I still get the same problems at runup. When I turn off the left mag, the engine starts to die. Turn on left mag, it comes back alive. I have double checked my p-lead/ground wiring.

Any tips out there, or should I just remove everything and try again from scratch tomorrow?
 
Does one mag have an impulse coupling? Did you rotate the crank past TDC, hear the coupling snap, then go back to 25 BTDC?
 
Mag voodoo

Does one mag have an impulse coupling? Did you rotate the crank past TDC, hear the coupling snap, then go back to 25 BTDC?

Yes, left mag has the impulse coupling. I'm sure I did do that, but honestly I did so many rotations/mag bumps today, I cant recall it all.

This is my first time trying to install mags, so I guess I should just start from scratch tomorrow.

Getting these mags installed correctly makes me feels like I need to get my voodoo doll out to make it all work.
 
I am trying to put my mags back on after a 500 our inspection on a Lycoming 0-360. My mags say left rotation and 25*. When I test run, the right mag is not working properly. Here was my install method:

1. I internally timed the mags with the timing pin in "Left" hole until it dropped onto the shoulder on the pin.
2. rotated prop to get compression on cylinder 1, then clocked the prop to put it at the 25* mark on my flywheel/starter marker
3. Installed the mag on the engine with the pin inserted, then removed the pin.
4. twisted the mag to where the buzz box would just turn on, then move back so it would just stop buzzing
5. Then I externally timed the mags to the engine using normal methods. The buzz box (left and right) lights up dead on at the 25* mark. Makes me think they are timed really closely.

I removed the right mag and rechecked the internal timing, but I still get the same problems at runup. When I turn off the left mag, the engine starts to die. Turn on left mag, it comes back alive. I have double checked my p-lead/ground wiring.

Any tips out there, or should I just remove everything and try again from scratch tomorrow?

Who did the inspection of the Mags? Were the breaker points re-timed by any chance?

Skylor
 
I would pull the cover of and confirm the alignment of the gears. Sounds like an assembly error. With the pin installed in the two L holes, the small gear should have the”L” pointing to the tab on the coil,then reinstall the cover. If it is timed correctly and won’t fire, something inside is wrong. Several things it could be
 
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Probably misreading your post, but, my timing box lights go "out"

when the points open.

Ron
 
2nd try

All good points, thank you all. I am headed back out to the airport now to try again today with your suggestions in mind.
 
My son and I had a similar issue with his O-320. We did it 2 times and then took the mags off of my plane. Same issue, so we swapped the harnesses - same issue. We were working on it till 3:00am because he was trying to leave for work in the morning. We finally gave up for the night. The next morning we removed the mags and started from scratch and the engine was perfect. I have no idea what we were doing wrong, but I know that sometimes it is best to walk away as you did.
 
Finished!

I would pull the cover of and confirm the alignment of the gears. Sounds like an assembly error. With the pin installed in the two L holes, the small gear should have the ”L” pointing to the tab on the coil, then reinstall the cover. If it is timed correctly and won’t fire, something inside is wrong. Several things it could be

I got my mags timed finally. As I said above, this is my first time doing this, so I have no idea if what I'm about to describe below had any impact on the timing, or I just somehow got them timed right after the 9th attempt of performing the same timing process (internal and external).

Here is what I did:
After doing several more re-times this morning to no avail, I opened up my right mag, and the small gear tooth with the "L" on it appeared to be one tooth off from directly vertical pointing towards the coil. So I rotated that small gear one tooth so the "L" tooth now pointed vertical to the coil. I also wiped off the grease that was smeared on the tab of the coil (that touches the large gear).

I then retimed timed the mag(internal and external), attached it to the engine, and voila, the mags are working properly.

Like I said, to be honest, I don't know what I did to fix it, or if I just finally timed it correctly. In any event, I do appreciate the input and ideas.
 
I opened up my right mag, and the small gear tooth with the "L" on it appeared to be one tooth off from directly vertical pointing towards the coil. So I rotated that small gear one tooth so the "L" tooth now pointed vertical to the coil.

Yes, this is what addressed your problem. Just one tooth off will leave the rotor too far from the post for the spark to jump. These mags have low spark energy compared to auto stuff and are intolerant of thing like rotor to post clearance being too large.
 
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It was a local shop to me. Lesson learned I guess. Next time I'll ship them to one of the well known magneto businesses for inspection.
 
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