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Mag timing on IO-540

Plummit

Well Known Member
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
 
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.
 
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.
 
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
 
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
 
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
 
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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