(Slick SB1-98, Lycoming SB 537)

Affects 540 engines with 5th order counter weights.

I am trying to figure out how to go about this service bulletin.
This is not a thread about whether or not you need to comply with an engine/magneto SB but rather the best way to deal with it.
It clearly affects our IO 540s and those with Slick mags.
A 250 hour inspection does not seem like a big deal but for me any SB is a nuisance and I am exploring my options.

1: replace the left impulse mag with a second EI.
2: replace impulse coupled mag with retard breaker magneto.
3: follow and comply with SB.

I've been talked out of dual EIs and I would prefer one mag and one EI anyway.
A retard breaker would be my preferred option, does anyone have experience with one of those instead of an impulse coupled mag?
I have no experience looking at the inner working of a mag and would possibly not see a potential problem. Sending it off typically takes the plane out of service for 2 to 3 weeks, not a disaster but if I can avoid it I would prefer not to do that.

I have a retard mag plus Slick start, starts fine. Of course it cannot be hand propped if the battery is totally dead.
Why not go to a mag with no impulse, no retard, and just start on the EI (only)?

Ernst, I may be wrong but can you simply change the Slicks to a newer version, or go Bendix

From memory your mags are different to mine, which are Mid- 08 vintage.

Bob, after 10 years of flipping both toggle switches for starting I am afraid I'll
miss that little detail one day and deal with the damage of a kick back.
The engine certainly starts easily with just the EI or the mag or as I do it on both.
The SB specifically recommends complying with the instructions OR
replace the impulse coupled magneto with Slick 6300 Series retard breaker and direct drive magnetos with a Slick Start magneto start booster.

For the life of me I cannot find out what a "retard breaker" is, even google is clueless. Is a retard mag an alternate form of impulse coupled mag?

RV10inOz
My engine and its components are less than 3 years old and Bendix mags have a rap sheet of SBs even longer than Slicks.

The good news is the engine has been running without a single hiccup and I am still 50 hours away from the 250 hour inspection interval. I am just trying to have good information before taking action on my magneto.
Thanks for the help

As a rule I prefer the redundancy of one electronic component and one mechanical component.

An impulse mag has a rachet and pawl mechanism, with a spring, so at low rpm (starting) the mag is held back, then suddenly released. This retards the timing to near TDC, and the higher speed increases the voltage, both good for starting.
The retard mag has a second set of points, which open at TDC. They are wired to a SlickStart ('shower of sparks') which supplies a high voltage to the mag, so again you have a boosted voltage at TDC for starting. When you release the start key you go back to the normal points at 25 or whatever it is for your engine timing advance.
I believe the SB calls for an inspection for loose or working rivets that hold the pawl arm. Sounds easy except you have to pull the mags, then retime them.

I would think you could wire a relay, controlled by your start button, to ensure that the 'wrong' mag was grounded. I have not thought thru failure modes, though.

Bob, that all makes more sense now.
I understand the workings of an impulse coupled mag and I now see there is
another mag called a retard mag essentially achieving the same thing for the purpose of starting without the mechanical impulse coupling, instead using a second set of points.

Google will still not bring up "retard mag" however and if I wanted to buy one of these, what would I call it and where can I get one?
Aircraft Spruce's website does not understand retard mag nor anyone else's.
Do you know the # for a retard magneto for an IO 540?

I may just stick to what I have and take the magneto off at annual for inspection. As you said, not that complicated.

I see we are almost neighbors, maybe we could talk over lunch sometime.

I'm not at the airport but the Slick application guide lists 6393 as the left, retard mag. And 6350 as the right, no retard or impulse mag. That's consistent with my memory.