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06-15-2015, 12:20 PM
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Join Date: Jul 2012
Location: Fresno, CA
Posts: 270
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impulse coupling
How can I tell for sure if I have impulse coupling on one or both Slick mags (model 6393 on left, 6350 on right)? There is no difference externally that I can see (both seem to sit on a thick aluminum color base between the mag body and the engine case. Related question is if I do have impulse coupling on both, how does the wiring of the start switch change?
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06-15-2015, 12:27 PM
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Join Date: Feb 2008
Location: Largo, FL
Posts: 1,029
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Retard Breaker Mag
I believe the 6393 is a retard breaker (non-impulse) mag ----- if that is what you have, I think you need a Slickstart hooked to it ------ very hard to start the engine without the Slickstart.
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06-15-2015, 12:36 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Slowly and carefully turn the prop by hand in the normal rotation direction. Stay out of the prop arc just in case it fires. As you come up on a compression peak, you will hear a distinct 'clunk' noise if you have an impulse coupling.
As previously stated, I believe you have a retard breaker (extra points open at TDC but no impulse mechanism). These are designed to work with a Slickstart unit.
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06-15-2015, 01:00 PM
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Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,393
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Mag Switch
If you have a mag switch with a start position and non impulse mag in right position the right mag terminal on the switch needs to be jumpered to the terminal immediately adjacent to the R terminal. This grounds the right mag when the switch is placed in the start position.
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06-15-2015, 01:49 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Don't do a Tim Allen
As always, the manufacturer's literature is the best source.
http://www.qaa.com/resource-center/R...on%20Guide.pdf
Magneto types (active and obsolete) are listed on the last few pages, with definitions on page 10.
6393 = RB = Retard Breaker
6350 = DD = Direct Drive
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Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
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La Cholla Airpark (57AZ) Tucson AZ
Last edited by az_gila : 06-15-2015 at 01:54 PM.
Reason: 6393 was mis-typed as 6390 - finger trouble...
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06-16-2015, 04:35 AM
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Join Date: Feb 2007
Location: Mpumalanga, South Africa
Posts: 1,065
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I have exactly this set-up and can confirm that you have a retard breaker on the left. You should be able to see an extra terminal for the Retard.
You will need a Slick Start:
https://www.championaerospacepubs.co...00-SL2-96G.pdf
Having said that, I believe you can use an old-fashioned vibrator, but why would you?
Set-up was easy with a timing box. You just set the advance timing and the retard timing is taken care of internally. I only have a few starts (cold and hot), but they have all been near instantaneous with no spluttering or hesitation - really sweet.
As far as I can tell, the only downside of not having an impulse breaker is that you can't hand-swing in the event of a flat battery. Call me unadventurous, but that's probably something I wouldn't want to do on an engine that size anyway!
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Paul
Mercy Air, White River FAWV
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06-16-2015, 07:08 AM
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Join Date: Jul 2012
Location: Fresno, CA
Posts: 270
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Thanks for all the help guys.
Guess its a slickstart for me....
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01-17-2016, 11:41 PM
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Join Date: Jun 2013
Location: Tucson, Az
Posts: 143
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retard breaker question
I have a Vans IO540 on my RV10. I have been flying it for about 18 months and have recently been having trouble starting it mainly when it is hot.
When i was building the plane I was not very knowledgeable about what a retard breaker (RB) mag is. In fact I thought I had an impulse coupling mag on the left side. I recently found out it isn't. It's a RB.
I have been learning more about the difference between mags recently but do not know how an RB mag that doesn't have the RB terminal connected to anything behaves.
I have been flying without a vibrator box or Slckstart on the left side. How does this affect my ability to start the airplane??
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Alan Muhs
Tucson, Arizona
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RV10 flying since July 2014- 700 hrs as of July 2020
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01-18-2016, 12:05 AM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Quote:
Originally Posted by awmuhs
I have been flying without a vibrator box or Slckstart on the left side. How does this affect my ability to start the airplane??
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Mostly the engine will have to spin fast enough for the mag to generate enough voltage to jump the plug gap. The slickstart or impulse couplings boost the voltage at very low rpm. So if the day comes that your battery is weak so the starter turns the engine slowly; or the plug gaps open up, it may not start.
Make sure your ignition key is wired so you start only on the retard breaker.
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01-18-2016, 06:16 AM
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Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,679
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Quote:
Originally Posted by BobTurner
Mostly the engine will have to spin fast enough for the mag to generate enough voltage to jump the plug gap. The slickstart or impulse couplings boost the voltage at very low rpm. So if the day comes that your battery is weak so the starter turns the engine slowly; or the plug gaps open up, it may not start.
Make sure your ignition key is wired so you start only on the retard breaker.
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That is exactly the way I have experienced it. I flew a plane that I thought had an impulse coupling and it only had the Retard breaker. It never failed to start cold. It only seemed to have a problem after refueling and trying to restart. I added a SlickStart and that solved the problem.
I'm sure there is a good reason why Van's only sells engines with the RB Mag, but doesn't include the necessary SlickStart box, but I can't imagine what it is.
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Jesse Saint
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