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Thinking about replacing left impulse mag on IO-540

molson309

Well Known Member
Hi all, My IO-540-D4A5 is subject to the AD regarding Slick impulse coupler magnetos. I recently removed it and the coupler seems to be good, but I am strongly considering replacing it with either a straight magneto or a RB one - I have a Lightspeed for the right magneto so the RB magneto would only be for redundancy.

I've found I need to remove the magneto adapter and install shorter studs, and remove the impulse drive gear while installing another gear on the magneto shaft. However, it's not clear 1) how to remove the impulse drive gear - it's inside the case, does it just pull out? - and what what the p/n for the magneto drive gear is. Aircraft Spruce lists one for the IO-540, LW-19096, but they want $1267.00 for it!
If it's this expensive to change over, maybe I will stay with the impulse mag and put up with the recurrent 250 hour inspections, but am a bit nervous about have the impulse coupling come apart and result an in emergency.

Any guidance here would be appreciated.

Thanks in advance!
 
I got through the process and am posting what I ended up doing to possibly help someone else that's also looking at doing this.

I had a Slick 6351 impulse mag in the LH position on my IO-540-D4A5 which is subject to recurring 250-hour inspections on the impulse coupler. Since it is a royal pain on my engine to remove the magneto - need to remove the oil cooler first - I decided to replace this magneto with a Slick 6393 retard breaker mag along with a SlickStart booster.

As I mentioned in my first message I thought I needed to replace the magneto drive gear in the engine with another. This was based on an exploded parts diagram I came across on the Internet, but was wrong. The drive gear is fine and will work with the 6393, but you do need to purchase a 73000 adapter to mount to the magneto. This works with the cushions already present with the 6351 impulse mag. The adapter costs over $200 new but can be found yellow tagged for under $100.

I was concerned about the potential of losing one of the mag drive cushions into the accessory case when installing the mag. I used heavy grease to hold them in place, but in looking at the opening it seems like it would be quite difficult (or unlucky) to have one actually drop into the case; the openings around the drive were quite small.

The SlickStart module makes the wiring quite easy compared to the vibrator style box needed otherwise. You run a new wire from the starter that's energized when starting, and wires from the P-lead, retard breaker post on the 6393, and ground from the 6393 to the module. No other wiring change is needed, the existing wires that connected to the impulse mag are connected in the same way to the 6393. The SlickStart box contains shielded wires and a fuse holder for the power wire, some assorted terminals and splices, so most of what you need for the wiring has been provided.

Finished the wiring, timed the mag, and the engine fired right off when started with only the retard breaker mag selected. I will have to see if hot starts are easier using this.

I now have more peace of mind with this system knowing there's no chance of a disintegrating impulse coupler causing damage to my engine.
 
I need to look into this as well since I an having issues with my left mag right now and have the same set up as you on my F1
 
How can I tell if my “backup” mag has the 73000 drive installed (versus the 73013 coupling)?
 

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How can I tell if my “backup” mag has the 73000 drive installed (versus the 73013 coupling)?

I've found it frustratingly difficult to locate any information as to what the difference between the two drive gears is. I did not look but a search may find an exploded parts diagram showing your magneto and the drive gear used to mount it to an IO-540. Hopefully it has the 73000 coupler and you can just pull it off and put it on your new mag.
 
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