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  #1  
Old 10-16-2013, 01:27 PM
John Courte John Courte is offline
 
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Location: Los Angeles, CA
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Angry Left timing pin in magneto and turned the prop - what now?

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
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  #2  
Old 10-16-2013, 01:39 PM
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rocketbob rocketbob is offline
 
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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.
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  #3  
Old 10-16-2013, 02:42 PM
Ron B. Ron B. is offline
 
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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.
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Old 10-16-2013, 02:49 PM
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rocketbob rocketbob is offline
 
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No you have to use the pin every time you time the mag.
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N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
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Old 10-16-2013, 02:49 PM
John Courte John Courte is offline
 
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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.
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  #6  
Old 10-16-2013, 02:53 PM
noelf noelf is online now
 
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The last two issues of KITPLANES magazine covered internal and external timing of mags.
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  #7  
Old 10-16-2013, 02:59 PM
Robert Anglin Robert Anglin is offline
 
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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
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Old 10-16-2013, 03:26 PM
Bavafa Bavafa is offline
 
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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?
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Old 10-16-2013, 03:48 PM
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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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N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #10  
Old 10-16-2013, 03:50 PM
John Courte John Courte is offline
 
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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.
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