RV-10 IO-540-c4b5 Slick magneto Fail!

When choosing ignition systems for my aircraft I am very cautious. When I rebuilt my IO-540-c4b5 I decided to go with the tried and true Slick mags. The left mag has slick start with retard points and the right mag is just a direct drive mag. On a trip just a few weeks ago I had a hard time starting the airplane. I thought that maybe I just flooded it or something. After getting the airplane started the mag check was fine and we went on our short trip. After spending the day in Louisville Ky we came back to the airport and loaded up everyone. The airplane was hard starting again. Once the airplane did start the mag check was ok and we went home. Well I had just about enough of not getting the airplane to start on the first try with my family on board. After talking to the Slick Tech Rep. We were convinced that the slick start had went bad. Ordered a new one, put it on and nothing. The same problem.
Ok! The left mag is coming off. Pulled the rear cap and behold the problem was that the cam was worn out! The one that opens and closes both the regular points and retard points was completely worn out after only 120 TT! Slick will not sell you just the cam so you need to buy the whole points kit. $90 later we are back in business. But I let my A&P brain get the best of me and decided to pull the rit mag to check on its condition. Shut the front door, it is worn badly also. Another $90 and a 30 mile round trip number 2 and we are good to go.
So from now on I will be checking my mags with removal every 100 hours. Carring a spare set of cams and points with me at all times.
The problem with this cam wearing out is that I could wear out in flight and cause the points not to open.if the points do not open the mag will not fire and the engine will not run.
I sure do wish I could get one of those 6 cyl P mags right now.

There was an SB on some Slick Mags for premature cam wear. You might want to see if yours fell under that SB.

I have bought just the cam and the cam grease for my 4 banger.

Jon, while you're at it replace mag gear bearing. Last I checked they were $21/apiece. Have seen a number of those disintegrate and make their way around the inside of the engine.

The other day a friend of mine was showing me his wife's new engine in her O-360 powered 172, and it had brand spanking new TCM mags on it. Personally I don't care for Slicks and will take a Bendix any day over one.

When I was taxiing out to depart SnF in my Rocket, I did a quick check the mag, (1 Electronic, 1 Mag) and the mag was dead... I taxiied back to the performer hangar and called Emergency Aircraft Repair. They brought an Ohm meter and some tools, we rung out the P-lead and it was good, so I pulled the Mag (off of a hot engine, Ouch) and the impluse coupling was in pieces.....

I went to the Champion booth in the vendor hangar and the Slick rep said that an impluse coupling should not be installed on a 5th order counterweighted engine ( -540-C4B5 The "5" here indicates 5th order counterweight) There is an AD on impulse coupling mags on Piper Pawnees and Britten-Norman Islanders...

Long story short, the impulse failure seized the mag, which shattered the Mag drive gear, which took a tooth out of the fuel pump idler gear....

Fortunately all the parts feel straight down in the rear part of the sump, and I airlined home, organized the parts, and went back a week later and fixed it.....

A Shoutout to Tailwheels Etc at KLAL... Great people... They helped me pull the engine and accy case, and put it all back together and when I was done, I asked them for a bill and they said, no charge... UNBELIEVEABLE... I left them a check anyway.....

The lesson is, if you have an impulse coupling on a 5th order counterweighted engine, the mag needs to be inspected with a Slick Go/no-go rivet gauge every 250 hours... I replaced my mag with a retard breaker mag. ( I already had a Slick-Start, so that was easy...)

Tailwinds,
Doug Rozendaal

F-1 EVO

Doug, or anyone else for that matter------------do you know if the Lasar setup has the impulse coupling, and if so, is it also subject to the same failure??

TC E-295 covers O 540A.B.D,E,F,and H. Almost all are 5th order counterweighted engines. Almost all of them call out an S6LN-21 (impulse mag) on the left side. Only a couple call for 'tardo mags.

Almost all of them call out an S6LN-21 (impulse mag) on the left side. Only a couple call for 'tardo mags.

Click to expand...

I take that back. I just looked and it's 50/50.

n700jl said:

I sure do wish I could get one of those 6 cyl P mags right now.

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Yeah - STILL waiting........

Doug,

I have the same set up (impulse with slick start) on the LH side with a normal straight slick on the RH side. I want to install the 6393 (retard breaker) on the LH side. The slick start connections are straight forward as outlined in the SS install instructions. (Only slightly different than the impulse hook up)

However, were you able to use a normal toggle switch on the LH mag like you did before? or was some other set up required?

EDIT: The answer is YES a toggle switch can still be used with the 6393 retard breaker mag. However the 6393 mag will need a different drive coupler as the impulse drive coupler is NOT compatible.

B25Flyer said:

When I was taxiing out to depart SnF in my Rocket, I did a quick check the mag, (1 Electronic, 1 Mag) and the mag was dead... I taxiied back to the performer hangar and called Emergency Aircraft Repair. They brought an Ohm meter and some tools, we rung out the P-lead and it was good, so I pulled the Mag (off of a hot engine, Ouch) and the impluse coupling was in pieces.....

I went to the Champion booth in the vendor hangar and the Slick rep said that an impluse coupling should not be installed on a 5th order counterweighted engine ( -540-C4B5 The "5" here indicates 5th order counterweight) There is an AD on impulse coupling mags on Piper Pawnees and Britten-Norman Islanders...

Long story short, the impulse failure seized the mag, which shattered the Mag drive gear, which took a tooth out of the fuel pump idler gear....

Fortunately all the parts feel straight down in the rear part of the sump, and I airlined home, organized the parts, and went back a week later and fixed it.....

A Shoutout to Tailwheels Etc at KLAL... Great people... They helped me pull the engine and accy case, and put it all back together and when I was done, I asked them for a bill and they said, no charge... UNBELIEVEABLE... I left them a check anyway.....

The lesson is, if you have an impulse coupling on a 5th order counterweighted engine, the mag needs to be inspected with a Slick Go/no-go rivet gauge every 250 hours... I replaced my mag with a retard breaker mag. ( I already had a Slick-Start, so that was easy...)

Tailwinds,
Doug Rozendaal

F-1 EVO

Click to expand...

F1R said:

EDIT: The answer is YES a toggle switch can still be used with the 6393 retard breaker mag. However the 6393 mag will need a different drive coupler as the impulse drive coupler is NOT compatible.

Click to expand...

I don't think this is correct.
A retard breaker mag requires something to physically switch between the run breaker points and the retard (start) breaker points while you are cranking.
This is normally done by using specific connections on the key style start switch. When the key is in the start position, it switches to using the retard points. This functionality would not be occurring if you were just using a simple toggle switch to control the P leads on the mags.

The retard breaker mag requires a slick start module. The Slick start can be configured to work with about 4 different magneto arrangements including an impulse mag, and detailed wiring instructions are provided with each Slick Start. The PDF version is on line.

Regarding the retard breaker mag, when the starter is energized to crank, the Slick start connects the TDC points(retard points) only as long as the starter cranks. ( The slick start also boosts the voltage and spark energy considerably, only while cranking)

When you let go of the start button the advance points are effective and all is normal.

I have a 540 C4B5 in a certified AC that works fine with a key start and a slick start with the factory supplied retard breaker slick LH mag.

I have a second 540 C4B5 in a rocket that uses a slick start on an older impulse mag that has been a solid performer. Two toggles. One for each mag. Works fine. Just start on the LH side only.

Scott at Aerosport kindly took the time to explain that a toggle can be used with a retard breaker slick mag and how it plays out.

The wiring hook ups for both mag types with Slick Start is clear enough. What is not as clear is that you can use a conventional toggle switch for the retard mag.

My wife has another AC also with a slick start and in all 3 cases they work great. So have our slick magnetos. I was only considering a scheduled inspection / overhaul of the impulse coupler vs replacing with a retard breaker mag for LH side of my homebuilt.

Well I learned something new....
I messed with a Slick Start many years ago (in fact it was a comp'ed unit provided for evaluation when it first came on the market)
I don't remember it having the ability to internally switch its output, but the installation I was using it on had an impulse coupling so I may have just ignored it, or maybe the design has evolved over the years.