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11-04-2017, 07:37 PM
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Join Date: Nov 2008
Location: Shreveport, LA
Posts: 1,002
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Seeking Mag Synchronizer Help
Not using the timing marks on the ring gear, nor using one of those contraptions you attach to the spinner, is there an easy way to determine top dead center (for magneto timing)?
Also, silly question, but for my sanity, the left magneto is the one in front of the pilot seat, and the right mag is the one in front of the passenger seat, yes?
I can not get my mag synchronizer to work at all.....I feel certain its operator error.
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11-04-2017, 08:07 PM
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Join Date: Nov 2016
Location: Navarre, FL
Posts: 385
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Seek the help of an A&P or someone familiar with the process. The ignition has to be ON for this, aka mags hot.
__________________
Shane
RV-6 IO-360 Angle valve, G3X touch
Murphy Moose M14P flying
Aero Engineer, A&P
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11-04-2017, 08:49 PM
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Join Date: Nov 2012
Location: Gilbert, AZ
Posts: 124
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Timing
The engine needs to be at 25 before TDC to time mags, assuming that's what the engine data tags says. Remove number one spark plug, turn over engine till it comes up to compression, you can carefully insert a screwdriver into to the spark plug hole and feel the piston move. Right at TDC you should hear the impulse coupler snap, this should be right at TDC. If you have a flywheel with 149 teeth, turn the prop backwards about 10.3 teeth, that should be 25 BTDC, but check my math. 360 degrees 149 teeth is 2.416 degrees per tooth. 25 degrees divided by 2.416 Is 10.34. But you need to know when the points move, so you really need the sync box. The two biggest errors are switch not on both and impulse coupler not snapped. The right left is as you are sitting in cockpit looking forward.
The left mag is usually the impluse.
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11-04-2017, 09:04 PM
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Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966
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Correct on the mag location I.D. Here is how to get very close to finding TDC without the ring gear or a dial gauge:
Leave ignition OFF
Remove all spark plug leads and all the top plugs. It’s now safe to rotate the prop.
Stick your thumb in the top empty spark plug hole of cylinder #1.
With your thumb firmly in hole and rotate the prop in direction of regular travel until you feel air blow by. You are now in the compression stroke of #1. Stick a 1/4” wood dowell in the #1 hole and hold pressure on it on top of the piston.
Continue rotation and you will come to a point where the dowell rod stops coming up and starts to go back down. You can rock the prop back and forth to get really close. Keep gear lash I’m mind as you need to stop the rotation when turning in the correct rotation, not going backwards. You can now install the ring gear to identify exact TDC using the TDC mark on the forward face of the ring gear with the .062” hole on the front of the starter, or use the aft TDC mark on the ring gear lined up with the case split.
Follow the directions that came with your magneto buzz box. With the plugs removed, there is no danger of an accidental start from rotating the prop and you do need the ignition turned ON to time it. If your still having problems with the buzz box not working and the internal battery is good along with correct lead locations, remove your p-leads and try again. Sometimes there may be a problem with them or the switch itself. Good luck!
__________________
David C.
Howell, MI
RV-10: #41686 Under Construction
RV-9A: #90949 Under Construction
RV-10: #40637 Completed/Sold 2016
Cozy MKIV:#656 Completed/Sold 2007
"Donor Exempt" but donated through Dec. 2020
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11-04-2017, 09:21 PM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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Quote:
Originally Posted by blueflyer
Not using the timing marks on the ring gear, nor using one of those contraptions you attach to the spinner, is there an easy way to determine top dead center (for magneto timing)?
Also, silly question, but for my sanity, the left magneto is the one in front of the pilot seat, and the right mag is the one in front of the passenger seat, yes?
I can not get my mag synchronizer to work at all.....I feel certain its operator error.
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This.... http://www.aircraftspruce.com/catalo...ickkey=3240965 IS the easiest way to find the TDC of your motor. The timing marks on the flywheel to the case are vague at best.
Get the proper tools and learn the proper procedures. Timing is very important......... Good luck.
__________________
VAF #897 Warren Moretti
2019 =VAF= Dues PAID
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11-05-2017, 05:09 AM
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Join Date: Nov 2008
Location: Shreveport, LA
Posts: 1,002
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Thanks for all the replies. I believe I am doing what everyone has described, although I may try the wooden dowel to feel TDC.
My mags are on ( toggle switches) and I find compression stroke of #1, impulse coupler pops, turn the prop backwards a little, and I walk around to the the ring gear, its right at the appropriate mark against the case. When I turn on my buzz box, I get nothing...I try and move the prop just a little in either direction and I still cant get a peep out of my buzz box.
It buzzes like crazy when I unhook one of the buzz box P-lead connectors from one of the mags, so I know my battery is good in the buzz box.
My A&P is coming today to complete my CI, but I thought I would try and time the mags before his arrival.
Last edited by blueflyer : 11-05-2017 at 05:24 AM.
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11-05-2017, 07:45 AM
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Join Date: Jan 2005
Location: Charlottesville, Virginia
Posts: 1,230
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wires
Only thing I might add to the already great replies is:
Check that you are indeed attaching the buzz box leads to the P-Lead terminal and not the ground terminal, as they are right next to each other and I always have to check myself when I am attaching mine.
Already said above but worth repeating:
Buzz box black lead to good ground.
Ignition/mags hot/on.
Another easily done problem is timing to TDC instead of 25 degrees.
No need to ask how I know about these issues 
__________________
Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
D100-KMD150-660-TT ADI2- AS air/oil seperator. Vetterman exhaust with turndown tips.
Louisa, Virginia KLKU N94TB
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11-05-2017, 09:39 AM
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Join Date: Oct 2012
Location: Clearwater, FL KCLW
Posts: 1,281
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Quote:
Originally Posted by blueflyer
Thanks for all the replies. I believe I am doing what everyone has described, although I may try the wooden dowel to feel TDC.
My mags are on ( toggle switches) and I find compression stroke of #1, impulse coupler pops, turn the prop backwards a little, and I walk around to the the ring gear, its right at the appropriate mark against the case. When I turn on my buzz box, I get nothing...I try and move the prop just a little in either direction and I still cant get a peep out of my buzz box.
It buzzes like crazy when I unhook one of the buzz box P-lead connectors from one of the mags, so I know my battery is good in the buzz box.
My A&P is coming today to complete my CI, but I thought I would try and time the mags before his arrival.
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The buzz box should be buzzing at 25* BTDC, not TDC, which is where it seems like you are expecting it to. Are you turning the prop back far enough to check?
Chris
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Chris Johnson
RV-9A - Done(ish) 4/5/16! Flying 4/7/16
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11-05-2017, 09:52 AM
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Join Date: Nov 2008
Location: Shreveport, LA
Posts: 1,002
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You could be right, I may not be turning it backwards far enough. I'll know this afternoon once the mechanic arrives.
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11-05-2017, 10:12 AM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Feeling with a probe is OK for getting close (like a couple degrees), but to know with any required precision a piston stop is required. Marks can be off, a piston stop is the only way to be sure.
It does not have to be done each time unless there are no other references (for timing or TDC) when calibrating/setting the spinner hat.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
Last edited by BillL : 11-05-2017 at 10:15 AM.
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