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  #1  
Old 07-24-2018, 10:20 AM
rvator10's Avatar
rvator10 rvator10 is offline
 
Join Date: Apr 2006
Location: Fountain Hills, arizona
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Default YIO-390-A3B6 Magneto Questions

The Lycoming website parts catalog shows the left magneto “Plane” Slick 4370 and the right magneto “Retard” Slick 4347.
What is the difference between the Plane and Retard magnetos?
Does this engine require the champion Slick Start (shower of spark) system?
If yes, which magneto would it connect to, the Plane or the Retard?
When "starting" the engine would both mags be on or just the left?
thanks
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  #2  
Old 07-24-2018, 01:18 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
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The Lycoming literature I got with my YIO-390-EXP10 shows the left magneto

66GC15SFNN LYCOMING MAGNETO-IMPULSE 4372

and the right:

66GP-0SANN LYCOMING MAGNETO-PLAIN 4370

(That's "plain" for non-impulse)

the impulse mag is usually on the left, at slow (starter) speeds it fires around 0 deg advance

The right mag is usually 'plain' without the impulse coupling and fires at whatever advance has been set (20 deg for the YIO 390)

The non-impulse mag should be off for starting to avoid kick-back due to the spark advance

I've got my mag switches wired so that the starter will engage only if the right mag is off

No slick start required
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Last edited by Jake14 : 07-24-2018 at 01:25 PM.
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  #3  
Old 07-24-2018, 01:36 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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If you have an impulse mag, no Slick start needed.
If you have a RETARD mag, then the Slick start should be attached to that mag.
You can easily tell the difference between the mags. Slowly and carefully turn the prop (normal direction) by hand. If you hear a metallic ‘clunk’ near top dead center you have an impulse mag. In either case, you should disable any ‘plain’ (neither impulse nor retard) during start.

Last edited by BobTurner : 07-25-2018 at 02:35 PM. Reason: Big typo, fixed with all caps.
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  #4  
Old 07-25-2018, 05:04 AM
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mike newall mike newall is offline
 
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So.....

If you have a standard wired 'Cessna" key switch which is L, R, B, S - when you go to start, does it ground the right mag ?
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  #5  
Old 07-25-2018, 12:50 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by mike newall View Post
So.....

If you have a standard wired 'Cessna" key switch which is L, R, B, S - when you go to start, does it ground the right mag ?
Most 172/182 Cessnas came with two impulse mags, so the answer is no. Most Pipers came with one impulse mag, one plain, so the answer is yes. There is an arrangement of jumpers on the back of the standard switch so it can be configured to do whatever you want it to do on start.

Last edited by BobTurner : 07-25-2018 at 02:42 PM.
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