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Old 06-09-2017, 08:33 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,382
Default IO-540/retard mag

Today I was checking out the new owner of a -10 in the presence of the builder. The plane had two toggle switches (on/off) for the mags. I asked the builder if the left mag was the retard one, and he replied that neither mag had retard points, but that was okay since both had shower of sparks. I guess he saw my odd look, because he became defensive, asked if I was an A&P. I advised the new owner to really find out what mags were there, and if they really had no retard points that there was a non-zero chance of a kick-back and broken gear teeth. What say you? Am I all wrong here?
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Old 06-09-2017, 09:32 PM
Jesse's Avatar
Jesse Jesse is offline
Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,636

I'd be willing to bet that one is a retard mag unless it has an impulse coupling. Best option is to pull the top cowl and have a look.
Jesse Saint (Saint Aviation, Inc. - VAF Advertiser)
RV Hotel (hangar, room, car) at X35 in north FL

Commercial ASEL/S A&P/IA EAA Technical Counselor

Dynamic Prop Balancing, Prebuy Inspections, Condition Inspections, Repairs and Mods, Injector Tuning, Airframe, Engine, Panel Upgrades, Ferrying, etc.
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Old 06-09-2017, 11:13 PM
eaglen92ce eaglen92ce is offline
Join Date: Oct 2009
Location: Chandler, AZ
Posts: 161

If either mag has an impulse coupling you should be able to hear it snap when pulling the prop through by hand (mags off of course!!). That would not answer which one it was though.
Bill York
Stellar Airpark (Chandler AZ)
RV-6 N477DH
Eagle II N92CE (sold)
Hiperbipe N777HT (sold)
PA22-160 N9322D (sold)
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Old 06-10-2017, 07:24 AM
RONSIM's Avatar
RONSIM RONSIM is offline
Join Date: Feb 2008
Location: Largo, FL
Posts: 850
Default Hard starts

Our new (OH) IO 540 for the RV-10 came with retard (no impulse), and no Slickstart -- took me over a year to figure out why our starts were difficult, and even impossible, when hot. Installed Slickstart and problem went away.

RV-10 Co-built, maintained, flown (sold)
RV-8A Maintained and flown (Sold)
RV-6A Bought and Flying (N177RV), upgrades $$$
IO360, 180HP/CS, AFS 5600T, D10A, G650, G430, G327, ADS-B, VIZ385 AP
Very Happy Contributor
Based at KCLW (Clearwater, FL)
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Old 06-10-2017, 11:34 AM
Lenny Iszak's Avatar
Lenny Iszak Lenny Iszak is offline
Join Date: Sep 2008
Location: Palm City, FL
Posts: 261

My engine came from Van's in 2009 with a straight and a retard mag. Never seen a retard mag before and looking into it I figured out that I needed a SlickStart for it to start reliably. Not sure why that wasn't included in the kit or at least offered as an option. Maybe it was and I overlooked it.

Technically you can hook up a SlickStart to a straight mag using the wiring diagram intended for impulse coupled mags, but that would be bad as there will be nothing to retard the ignition. Not good.

I'm with Jesse, he most likely has a retard mag. At least I hope so
If he really has two straight mags with shower sparks, he's got a more thorough inspection to do...
Lenny Iszak
Palm City, FL
2014 RV-10, N311LZ - 450 hrs

Last edited by Lenny Iszak : 06-10-2017 at 03:59 PM. Reason: spelling
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Old 06-10-2017, 03:00 PM
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awmuhs awmuhs is offline
Join Date: Jun 2013
Location: Tucson, Az
Posts: 132
Default Slick start

I had same experience as RONSIM. I do not understand why there isn't more info on slick start provided with the Vans IO540 engine configuration.
Alan Muhs
Tucson, Arizona
Dues overpaid December 20, 2017
RV12 Southern Arizona Teen Aviation: wings, empennage & tail cone completed. Fuselage 70% complete
RV10 flying since July 2014- 475hours as of May 2018
RV6A purchased and flying
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