Magneto Thoughts

[druidjaidan]

We have a mildly rough running left mag. Between my mechanic and I we've done a bunch of diagnosing, but not found an obvious "this is what's wrong" issue. Plugs check out, leads check out, and the mag when disassembled meets spec. However, there are lots of visual signs of wear, and we are well over the 500 service bulletin so it makes sense to assume it's the issue.

He gave us three options:

1. The fastest option: He can replace points, condenser, gears and block. However, he can't sign it off as a 500 inspection, not that we're required to.

2. The apparently cheaper, but much slower option.  Send it out for a 500hr.

3. Get an overhaul exchange magneto.  Most expensive, but less that .5 AMU more than having him do the work and we get papwerwork for it being 500hr.

I'm kinda leaning toward the exchange, as we're valuing getting in back in the air quicker at this annual and the exchange seems like closer to a sure thing. Anyone offer an opinion?

[EricJ]

8 minutes ago, druidjaidan said:

We have a mildly rough running left mag. Between my mechanic and I we've done a bunch of diagnosing, but not found an obvious "this is what's wrong" issue. Plugs check out, leads check out, and the mag when disassembled meets spec. However, there are lots of visual signs of wear, and we are well over the 500 service bulletin so it makes sense to assume it's the issue.

He gave us three options:

1. The fastest option: He can replace points, condenser, gears and block. However, he can't sign it off as a 500 inspection, not that we're required to.

2. The apparently cheaper, but much slower option.  Send it out for a 500hr.

3. Get an overhaul exchange magneto.  Most expensive, but less that .5 AMU more than having him do the work and we get papwerwork for it being 500hr.

I'm kinda leaning toward the exchange, as we're valuing getting in back in the air quicker at this annual and the exchange seems like closer to a sure thing. Anyone offer an opinion?

An exchange sounds like a good option to me if you're valuing minimizing the down time.

[Andy95W]

Install a Surefly.  A little more money than an overhauled exchange but hot start issues will be a thing of the past and 500 hours from now it will pay for itself by not needing another inspection.

[Marc_B]

14 minutes ago, Andy95W said:

Install a Surefly.

+1. That’s what I did. Upfront costs, but a wash in the long run and some increased reliability benefit. 

[Ragsf15e]

I have a surefly too, but it isn’t “free”.  You’ll need to remove interior and run a power wire to the battery.  You also might need a new harness to match the SF.  That being said, I like mine.

if you keep the mag, just do the exchange.

[KSMooniac]

Can you run the same mag on either side of your engine?  If so, consider buying a 3rd and installing it now, then send out the existing one for 500 hr and save it for the next service interval.  Rinse and repeat.  

or go electronic.    

[druidjaidan]

Surefly is an interesting option, but I'm a bit nervous about going electronic ignition. f you look through my post history you'll learn why I'm leary about going to electronic ignition. It's just a one off, obviously, but My 2016 trip to Oshkosh would have been significantly more painful had I had Surefly

[EricJ]

45 minutes ago, KSMooniac said:

Can you run the same mag on either side of your engine?  If so, consider buying a 3rd and installing it now, then send out the existing one for 500 hr and save it for the next service interval.  Rinse and repeat.  

or go electronic.    

Often the mags themselves are the same part number, but one has an impulse coupler and the other doesn't, so they're not really interchangeable.    I always thought a good way around this would be to put an impulse coupler on each, so a spare with one would substitute for either.    You'd also get double the starting spark, which is nice (dual mags do this, too).

[A64Pilot]

7 minutes ago, EricJ said:

Often the mags themselves are the same part number, but one has an impulse coupler and the other doesn't, so they're not really interchangeable.    I always thought a good way around this would be to put an impulse coupler on each, so a spare with one would substitute for either.    You'd also get double the starting spark, which is nice (dual mags do this, too).

Some engines have dual impulse couplings, my 1946 C-85 does and it even has an odd different timing for each mag. 2 degrees different from memory

I had always assumed one was deleted as a cost savings?

I too am leery of electronic mags, they should be dead reliable as in never, ever fail, but that doesn’t seem to be the case? Seems I’ve seen quite a few posts about problems.

[N201MKTurbo]

3 minutes ago, A64Pilot said:

Some engines have dual impulse couplings, my 1946 C-85 does and it even has an odd different timing for each mag. 2 degrees different from memory

I had always assumed one was deleted as a cost savings?

The O-300 in my Cessna is the same way. One mag does all the tops and the other does all the bottoms. I tried all of them timed to 26, and 28, and with the split. It runs better with the split.

[A64Pilot]

18 minutes ago, N201MKTurbo said:

The O-300 in my Cessna is the same way. One mag does all the tops and the other does all the bottoms. I tried all of them timed to 26, and 28, and with the split. It runs better with the split.

And you get a different mag drop on run-up too, makes you wonder why the different timing.

Does it act like one longer spark?

[N201MKTurbo]

4 hours ago, A64Pilot said:

And you get a different mag drop on run-up too, makes you wonder why the different timing.

Does it act like one longer spark?

I think it has to do with airflow in the cylinders.

[jamesm]

4 hours ago, druidjaidan said:

I'm a bit nervous about going electronic ignition.

I get the scepticism. I had put the SureFly installed  and had the Right Magneto overhauled at the same time.  But to ensure that mag was overhauled was tested on the test bench before flying it. The SureFly ignition is same people who  brought us Plane Power alternators and Skytec starters so they a great reputation. I had one problem with the Skytec starter about 5 years ago the housing started become lose after over 18 years of use. initial installation of the SureFly of finding gear orientation during installation. I have no to little problem with SureFly/Plane Power/SkyTec products. The products design back in the 1940's have problems too. I guess pick your problems and try to minimize bad results.

Just my experience.

James '67C

[hammdo]

SureFly on the pilots side, overhauled mag on copilots side - 3 years and really like it. I had an alternator failure during ifr flight, declared and landed with no issue.  Having a SureFly does require an operable electric system - so I didn’t dilly-dally.

I kept one mag so I have something that didn’t require an operating electric system… SkyTec starter too…

I’d still do the SureFly again…

-Don