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Left timing pin in magneto and turned the prop - what now?

J

John Courte

Well Known Member
I've been debating bringing this up here, because it's truly embarrassing and the kind of thing that doesn't reflect well on my skills as a builder.

Last Saturday when I was retiming my mags (rt mag way off, lots of afterfiring) I left the timing pin inserted in the distributor block when I went to pull the prop through for buzz box timing. At this point, the right mag is totally inop. No backfiring or other indication that it's even working at all.

The "timing pin" in question was only a 3/32 pop rivet, but it was bent up pretty good when I finally extracted it.

What happens now? Have I ruined the magneto and just bought myself a $1000 lesson in checklists and details? In your experience, what's the usual damage from this kind of event?

thanks,
-John
 
At the very least you will need a new distributor gear, maybe the whole distributor block. So at least $180 or about $300. Ouch. This is very easy to replace and does not require internally retiming the mag but I would check it while it was open.
 
Just trying to learn from others so I will not have to pay for repairs. Did you have the mag. off from it's mounting pad? I thought the only time you needed to insert this pin into the mag. was when the mag was removed? For just timing adjustment the pin (different pin) goes into the starter mount and acts as a pointer on the flywheel. Am I missing something, then again there are probably setups with different mag. manufacturers.
 
You set the engine to 25* BTDC (yours may be different), then attach the magneto with the pin inserted into the mag so the timing doesn't slip while you're getting the gears to mesh. Once the mag is on, you pull the pin out.

I missed that last step.
 
Half full!

I see this as good that you will beat yourself up over this. If you didn't I don't think I would think well of flying with you. This is a good time to get to know the insides of your Mag. The distributor block and or gear can be changed on the bench. And you will be better for it to change out a set of points and get to set them too. The glass is half full on this one as you can offset this cost with the value of what you can do with the knowing how down the road when you have to service these things. Yours as always R.E.A. III #80888
 
Am I missing something here? The way I have been timing my mags is that I set my prop to 25 degree mark at TDC and loosen the nuts on the mag just be able to turn/move them ever so slightly to get it timed just at 25 degree.
I thought the pin is required only if the mag is being removed from the engine.

Have I got this wrong?
 
Why would you time a mag without taking it out first to inspect it? I guess in that respect I always use the pin. Or on a Bendix the tool used to lock the distributor gear. But yes you have to take it out once you start bumping the mag to time it, otherwise it will get bent like the OP stated.
 
No, you're not missing anything.

I left out the part of the story where I had pulled the mag off the engine to verify that it was engine-timed properly. Given the amount of afterfiring and the fact that it ran unsustainably rough, I thought it was a good idea to check.
 
Mag timing

John

You are right on that you use the pin to set the mag for inserting it in to the engine. Then you final time with a timing buz box not the pin.

As you have learned the hard way is that to insure that you remove the pin as soon as the mag is bolted to the engine.

I would recommend that people that have not been trained on mag installs and timing that they get with a experiences A&P mechanic and get trained on the process correctly.
 
jc11378 said:
John

You are right on that you use the pin to set the mag for inserting it in to the engine. Then you final time with a timing buz box not the pin.

As you have learned the hard way is that to insure that you remove the pin as soon as the mag is bolted to the engine.

I would recommend that people that have not been trained on mag installs and timing that they get with a experiences A&P mechanic and get trained on the process correctly.
Click to expand...

I have always followed this process, to adjust timing without removing it as I am not qualified to do any repair or inspections.

Now, soon I will need to send these for the 500 hour overhaul. Can someone share what would be the process for doing that kind of work? At the repair shop they will certainly pull the pin out to do the work. How would I get it back to the original timing that it needs to be before installing it.
 
Bavafa said:
I have always followed this process, to adjust timing without removing it as I am not qualified to do any repair or inspections.
Click to expand...

If you find it needs to be readjusted, that is because something internally has worn and needs to be inspected. The timing should not change unless there is a problem with the cam or points.
 
And will he who has spent a lifetime working on airplanes and DOESN"T have at least one bent pin in their toolbox please raise their hand? :eek:

noelf said:
The last two issues of KITPLANES magazine covered internal and external timing of mags.
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Which is why I asked Dave Prizio to write the articles you have seen in KP. It is funny that there are a number of very routine maintenance tasks that builders who maintain their own planes need to know - but don't always get exposed to during their build. Hence, the "Maintenance Matters" articles in Kitplanes.
 
rocketbob said:
If you find it needs to be readjusted, that is because something internally has worn and needs to be inspected. The timing should not change unless there is a problem with the cam or points.
Click to expand...

You are correct that if the timing is off something has worn, if the timing is advanced the points have eroded faster than the cam, if the timing has retarded the cam has eroded faster than the points.

You are wrong to state that this means that there is a problem with either points or cam. The manufacture has told me that they try hard to make the cam out of a material that will wear at the same rate as the points but that this is hard to do and timing drift, especially advancing is normal and especially in the first 100 hours or so of life on a new set of points.

I would be more likely to pull a mag for timing retarding then for advancing. Timing retarding means the point gap is getting smaller, if this continues you?re going to have a problem, if it advances 2 or 3 degrees the first year I?m going to leave it and just externally re-time it, if it continues advancing the next year I would probably pull and inspect it, if nothing is wrong re-time (set point gap) and re-install.
 
Russ McCutcheon said:
You are wrong to state that this means that there is a problem with either points or cam.
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Difference in opinion, I pull them off, inspect, and internally retime them. It takes all of 10 minutes to do. The other reason I pull it off is to look at the brush. They will operate normally but be full of carnage in the distributor block as the spark jumps across the dust that accumulates and melts everything. Only way to know for sure is open it up. A few years ago I inspected the mags in the Saratoga I flew my family around in and was quite shocked to find both mags had bad carbon brushes even though it was not in the serial # range specified by the AD. Glad I did because both were close to imminent failure.

I have the $$ T-100 tool kit and its rare that the rotor has to come out unless it needs seals or bearings. The rest can effectively be inspected with a screwdriver. They're dirt simple and I highly recommend people learn how to work on them.
 
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I'm not interested in joining the internal inspection debate... I personal use judgment based on how much the timing has drifted and how many hours since new or the last 500 hr inspection. If time is low and drift is minimal, I will re-time without opening up the mag.

What I wont do... Retime without pulling the mag off the engine and installing a new gasket.
Lyc's are hard enough to keep dry as it is. Breaking the seal on a mag and retimeing without installing a new gasket is a guaranteed oil leak from my experience.
 
Thanks for the advice and opinions, everyone. This weekend, I'll pull the magneto, open it up, and see what I'm in for.

I know of at least one A&P who hangs out at OXR, if he's there on Sunday, I'll see if I can borrow some of his time.

I'm going to to make it a point of pride to do this properly, even if I wind up aiming the money cannon at ACS for a set of P-Mags sometime down the road. It seems to me that I should know and understand all aspects of what keeps the prop spinning, at least to the point where I know to back away slowly, put the tools down, and call a professional.
 
Silver lining. There's a chance your mag was trashing to begin with. Hence the way out timing. Maybe you just got to retrash it and now you can dig in and fix.
 
rocketbob said:
Difference in opinion, I pull them off, inspect, and internally retime them. It takes all of 10 minutes to do.
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Dang, I need to come visit you so you can show me how to pull a mag, inspect it, set the points, reinstall it, set the timing in just 10 minutes :eek:

(Sounds like a boss I once had, no matter what it was, "it's a 10 minute job")
 
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rvbuilder2002 said:
I'm not interested in joining the internal inspection debate... I personal use judgment based on how much the timing has drifted and how many hours since new or the last 500 hr inspection. If time is low and drift is minimal, I will re-time without opening up the mag.
Click to expand...

We're on the same page on this one.
 
rocketbob said:
Why would you time a mag without taking it out first to inspect it? I guess in that respect I always use the pin. Or on a Bendix the tool used to lock the distributor gear. But yes you have to take it out once you start bumping the mag to time it, otherwise it will get bent like the OP stated.
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What if I take my mag straight off and install it straight back in, do I need to re- time it? When installing some fittings on my new Superior O-320, before mounting it to the engine mount, I had to pull the right mag for access. I marked the rotation with a pen and installed it back in the exact location (+\- 1/64" I suppose). Do I need to re time. Should I plan to time both mags anyway before first start?
 
Yes!

Dbro172 said:
What if I take my mag straight off and install it straight back in, do I need to re- time it? When installing some fittings on my new Superior O-320, before mounting it to the engine mount, I had to pull the right mag for access. I marked the rotation with a pen and installed it back in the exact location (+\- 1/64" I suppose). Do I need to re time. Should I plan to time both mags anyway before first start?
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Yes you need check it,,,,, even if you got it back in on the same tooth it will be out of time.
 
Slick Mag

If you contact Joe Logie at Slick Ignition Products and tell him the true about how you made the mistake there is a good chance that he will send you a new part for free or at a reduced cost [email protected]. They like to here the true. They don't like to see parts returned, stating they were received in the misfortune state.
 
Russ McCutcheon said:
it takes me more then 10 minuets just to get it off the engine:rolleyes:
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It takes me about 1 min. Seriously. Three screws to remove the cap/harness, 1 nut for the p-lead, take the two nuts off, yank it out. Done.

My main point is, its easy to do the job right and not spend very much time doing it.
 
It's interesting to me that every time I have a costly issue, there is a post about it on the forums. Yesterday, my adopted son and I replaced worn out mags with new ones. He is an AP who teaches at Baker Aviation School in Miami. Pat told me that at least twice a year a student will break off the timing pin inside a mag while installing. My take on that is that it is just a bit of carelessness. The pin that comes with the mags is quite large and shiny so it is easily seen. As soon as the mags were mounted, the pin was removed. It took us the better part of an hour to get both mags to light up on the buzzbox at exactly the same moment. (He is kind of anal that way) We spent about 4 hours on the total installation including a new harness and some extraneous hanger talk. Strangely, the old mags seemed to function normally at run-up and in flight. Upon inspection by our mag specialists, we were informed they were economically beyond repair. The repair station didn't have any reason to fudge on this inspection because they don't sell mags, they only repair and inspect. I wasn't charged anything for the inspection. A side note-The only reason I didn't purchase P-mags is because I have had such good luck with Slicks and I see that the electronic units don't seem to fare any better as far as repairs, etc. If only the electronics operated as well as automotive units. JMTCW
 
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