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-   -   Mag timing on IO-540 (https://vansairforce.net/community/showthread.php?t=169463)

Plummit 03-08-2019 07:31 AM

Mag timing on IO-540
 
I just had my mags (Bendix 1200 series) overhauled by Aero Accessories in
Van Nuys, CA. Installing them last night, I was unable to get the right mag timed perfectly due to it hitting the standby Alternator. I need to be able to move it a tad more up to get it to sync with the left mag at 25 BTDC. Anyone run into this? I'll call the mag shop when they open but thought I'd throw it out there for now.

-Marc

Carl Froehlich 03-08-2019 07:32 AM

Take the mag out, turn the gear a little in the direction you need, reinstall the mag and time.

Carl

Plummit 03-08-2019 07:41 AM

Quote:

Originally Posted by Carl Froehlich (Post 1330103)
Take the mag out, turn the gear a little in the direction you need, reinstall the mag and time.

Carl

Bendix mags go into a slot, not a toothed gear. I'm not sure how to clock it differently, other than 180 out.

-Marc

Carl Froehlich 03-08-2019 08:09 AM

Sorry - brain fart.

Carl

rocketbob 03-08-2019 08:19 AM

If you have the tool to hold the distributor gear on the red mark, you can turn the gear another tooth and put the holder tool back in to get the mag to clock differently in relation to the stud holding it onto the engine.

Toobuilder 03-08-2019 08:28 AM

The drive gear in the case can also be re indexed to get the slot where you need it. It should pull out fairly easily, but be cautious about dropping the bearing into the sump.

lr172 03-08-2019 08:30 AM

Quote:

Originally Posted by Plummit (Post 1330107)
Bendix mags go into a slot, not a toothed gear. I'm not sure how to clock it differently, other than 180 out.

-Marc

The slot is in a sub-component that has a gear on the other end of it. It has a pilot bearing loosely holding it into the case. Pull that assembly out and clock that slotted sub-assembly. Be sure to use the pin in the mag when installing.

Larry

vic syracuse 03-08-2019 05:29 PM

You've already got great advice here. The gear assembly can be pulled out and turned. However, pull out the rubber cushions first so you don't drop them into the crankcase.

Vic

N319BC 03-08-2019 05:36 PM

Quote:

Originally Posted by vic syracuse (Post 1330241)
pull out the rubber cushions first so you don't drop them into the crankcase.

Vic

Absolutely, I learned the hard way. :mad: Not an enjoyable experience.

john

Plummit 03-08-2019 10:35 PM

Update
 
I was able to get the mags really close but I want exact. It will get us to the Ice Cream Social tomorrow, but the next time I have the cowl off I will index the mag drive around to be able to get the right mag perfect.
Thanks everyone for your advice! I'll find out the details and post an update when I get 'er done!

-Marc

Plummit 03-10-2019 09:08 AM

Updated mag drive gear
 
In my searching for information on the Bendix mag drive I came across this service instruction regarding the drive-gear cushions:

https://www.lycoming.com/sites/defau...dification.pdf

-Marc

Plummit 09-08-2019 05:46 PM

Update
 
Well it's annual inspection time so I decided to tackle that pesky mag again. The mag came out fairly easy but the drive required some finagling to get it out.

Once out and the gear clocked back 1 tooth, it required even more finagling to get it back in. We finally resorted to some light taps with a small ball-peen hammer. Once the bearing was perfectly aligned with receiver, it slipped right in. Timed the mags, test ran the engine and Viagra! It worked great!
Thanks to all for the advice, and since I didn't drop the rubber cushions or bearing in the accessory case, I'm gonna make another contribution to the forum -it's worth it!

-Marc


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