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magento install/timing questions

ac_oldman

Active Member
I know the timing pin is removed prior to rotating the prop. Is it to be removed prior to rotating the magnetos for timing as well? I'd imagine so, but there's a post on this site that says otherwise.

Is it safe to keep the spark plugs in all but the #1 cylinder while timing magnetos, provided the wiring harnesses are both disconnected? will it damage a magneto to be timed while the wiring harness is disconnected?

Is it really a requirement to snap the impulse coupler prior to timing if you're doing a fresh install, prepped the prop to -25deg TDC prior to the install, and the mags agree with the prop timing mark?
I think snapping once timing is set to verify the IC retard is required.
any harm in snapping with a disconnected wiring harness?

test "bench timing" two mags, initially roughly timed with the pin in then removed, their grounds connected to each other and a buzz box should behave identically to timing once installed, correct? just to get the hang of it.
 
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Magneto install

Maybe you can find someone local to walk you through the process? It isn't hard but I can tell from your questions you could use a little training. I wish I was closer to you, would be gald to help.
 
Agreed! I do have someone who's helping me, this is prep work .
The kitplanes guide is excellent! However, I haven't found any written answers to any of the above - always good to have more information available for myself and others.

Sometimes there's disagreement between people who are familiar - for example, the timing pin question, where different posts seem to say different things.
Do you have any of the answers? :)
 
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Maybe you can find someone local to walk you through the process? It isn't hard but I can tell from your questions you could use a little training. I wish I was closer to you, would be gald to help.

Agree completely. It?s not complicated, but experience is required.
 
Keep in mind that the mags you are playing with are minimum $1000 each and a pin inadvertently or otherwise left in while the engine is rotated will destroy that mag . Take the advice given by above posters and it will be the best money you spend.
 
Pin is used for initial placement of mag on engine. It should be removed before timing or rotating the engine or the mag.

Larry
 
there have been several people killed by prop strike while timing mags. pull one spark plug from each cylinder before beginning.
 
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but if the wiring harness is disconnected from both mags how can it fire?

how does removing 1 from each help - wouldn't you need to remove both?
 
oh, I think I finally figured it out. spark plug out == no compression, even if you have one spark.

But I still think my no-harness-connected would work fine.
 
oh, no it wouldn't - there's a chance re-attaching the wiring harness might twist the magneto, so you'd want to check the timing again... except this time your harness is live.
maybe disconnecting all the leads would be easier than removing the plugs.
(though I will likely remove the plugs - no point risking it vs convention).

edit: yeah, what the heck would I do with the disconnected leads that will have a huge potential on them and potentially break the magneto if shorted. bad idea. convention.

edit: I understand the confusion now - when I said "leads" in this post, I meant the ignition harness to spark plug connections, not p-leads. I could understand why people would think this is crazy stupid.
 
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oh, I think I finally figured it out. spark plug out == no compression, even if you have one spark.

But I still think my no-harness-connected would work fine.

One of the reasons to take one plug out of each cylinder is that it keeps you from having to fight any compression from other cylinders as the prop is moved to find compression on cylinder #1 along with moving it back to come forward to remove gear lash after snapping the impulse coupling while timing.
 
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I love these kinds of postings

Makes me feel like I'm smarter than I think.
 
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I'm reinstalling my mags (returned from Champion for SB work) tomorrow morning. As mentioned removing the plugs relieves the compression build up so it's easier to turn the prop/crank for timing. Your mag wiring harness cap will be removed from the magnetos for internal timing (pin insertion) anyways so you're already doing what you are asking. Leave the harness off until all timing to the engine (mag clocking) is done. Here's a video example for timing slick mags for reference.

https://www.youtube.com/watch?v=0l96NU8afPM
 
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but if the wiring harness is disconnected from both mags how can it fire?

how does removing 1 from each help - wouldn't you need to remove both?

If you have the wiring harness (P-leads?) removed from both mags, both mags are HOT!!

Get some help.
 
Safety first, ALWAYS. It takes no time and no brains to remove one plug from each cylinder. Then, you can rotate the prop with no worries. And unless you are certain that the impulse coupling has snapped, you'll need to rotate the prop through to fire the impulse couple and then set #1 at whatever your timing mark is for the engine ( 25* BTC ). Be CERTAIN that the pin is removed after mag installation and don't rotate the prop until the pin is out, or like was previously pointed out, you'll trash the mag. Getting a little guidance from somebody that has been down that path will benefit you tremendously.
 
Safety first, ALWAYS. It takes no time and no brains to remove one plug from each cylinder. Then, you can rotate the prop with no worries. And unless you are certain that the impulse coupling has snapped, you'll need to rotate the prop through to fire the impulse couple and then set #1 at whatever your timing mark is for the engine ( 25* BTC ). Be CERTAIN that the pin is removed after mag installation and don't rotate the prop until the pin is out, or like was previously pointed out, you'll trash the mag. Getting a little guidance from somebody that has been down that path will benefit you tremendously.

After the impulse coupling snaps, rotate the prop backwards past the timing mark a few degrees and then ease it forward again to the timing mark. This removes the gear lash. If the prop was merely backed up to the timing mark it will be off by the gear lash.
 
seems erratic, could be another Earl.

At least this Guy is listed as owning an RG-3B in San Francisco. The RG could easily be a misprint instead of RV because the "kit manufacturer" is listed as "Vans Aircraft Inc".
 
wow.

Wow, I came asking for safety information and how not to damage things and got a pretty condescending response. Thanks to the people who actually helped. BTW the magnetos are re-installed and timed properly thanks to the people who gave me good information and an A&P.

The RG isn't a misprint it's the initials of the builder who decided to put his spin on the model name. The kit is still identified as an RV-3B kit.
 
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You know, some of these condescending remarks might be a result of being trapped at home frustration. People seem to have a slightly shorter fuse than normal and more time to play on the computer.

Just one observation.
 
On a positive note, this whole experience makes me really appreciate E/AB.

As a result of timing the magnetos, I now understand mags and ignition better, why you only start on the impulse coupled magneto, why I check for disconnected p-leads prior to shut down, one potential reason for RPM drop differences on mag checks, and what a mistimed magneto really means and how it could be damaging to an engine.

I'm definitely a better pilot as a result.
 
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