changing gasket on slick mag

ive got a n oil leak from my slick mag and need to change the gasket

i was hoping to mark the position of the mag, remove carefully so as not to disturb the gear and replace the mag, reinstall and job done

My inspector says no, we have to use a pin to lock the mag and then remove, replace gasket, refit and re-time.

I dont see why the mag needs the pin installed for removal - what am i missing here? I did purchase a bendix pin just in case, but why create extra work?

Proper Ignition timing of your engine is really important for optimum performance. Having the timing off just a few degrees can mean the difference between normal or high CHT's, especially at high power such as during take-off and climb.

The chances of getting it back EXACTLY where it needs to be just by marking it are very slim. Use the pin. It really doesn't add any extra time to the operation.

Vic

If you are asking IF your idea could work, I would say 1 in 10 chance, tops on an operating engine in a mount. Tops.

It is not the right way to do it. Your mechanic, family, friends and insurer wish for you to do it right.

Timing

The others are right. The odd of getting it back on in the same
place are slim. It may not properly timed now, drift is normal as the internals wear.

Don Broussard
Rv9 Rebuild in Progress
57 Pacer

Find a friend who can show you

Its not that tough. Find some who can help you and teach you how. Part of EAB is to learn something.

Cm

The pin only goes in when #1 is TDC on the compression stroke. Much easier to pull the mag, put #1 at TDC on compression (markings on ring gear), put pin in mag per instructions, install mag and re-time. The pin has slop and will allow variance of at least 5+ degrees. Always re-time after installation. The pin is designed to get you in the area, not to provide precise timing. I see no benefit to spending 20 minutes rotating the engine back and forth to get alignment, just to put the pin in before removal. That steps adds no value. Getting the pin in when off the engine takes 30 seconds. Also, the pin engages in a plastic gear. If you are swing the prop back and forth trying to get the pin in while doing so, you run the risk of cracking the two plastic parts. A bad idea.

The marking method doesn't help to insure the gear goes on the same way it came out. Not worth the risk of backfiring and other issues.

Also suggest that you use a gasket dressing on mag side of gasket. It reduces chances of leaks, while still allowing adjustment.

Larry

david.perl said:

I dont see why the mag needs the pin installed for removal - what am i missing here? I did purchase a bendix pin just in case, but why create extra work?

Click to expand...

It doesn't, but the mag can't be accurately reinstalled without locking then mag position during re-installation and then fine tuning the timing using a magneto timer.

Correction to Larry's great post above, engine should be set to the manufacturers recommended timing BTDC on #1 compression stroke , not TDC.

Gusmax said:

Correction to Larry's great post above, engine should be set to the manufacturers recommended timing BTDC on #1 compression stroke , not TDC.

Click to expand...

Thanks for catching that. Composed my thoughts too quickly

Larry

Gasket

We do it all the time, use a fine scribe to mark
It and before
Removal make sure it looks right. Little sealant on
New gasket and don?t move anything. If there?s no
Room then we just plan on retiming it. Again if you
Have room very possible.

Timing

Seven posts NO ONE has questioned whether or not this is an impulse mag.

In theory it should work. I say try it.
When done with the pin, you remove the pin prior to installation, so all it does is give you a good starting reference - which you will already have before you remove yours.
Having said that, it is likely that you will accidently turn it during removal or installation. If you get it aligned with the right gear tooth and use your mark, it will be correct.
Do you have a mag synchronizer? I assume not since you asked the question in the first place. Even if you do it this way, I would want to confirm synchronization afterwards.

I've done something similar dozens of times on several EZ's - but not for the same reason as the OP. Most EZ's don't have enough mag to firewall clearance to permit removal/installation of the harness - so...

? mark location of mag case relative to the accessory case with a Sharpie or scribe
? while NOT moving the prop, carefully remove the mag with harness cap intact
? while not moving the mag (or prop), install new gasket and reinstall the mag with the nuts hand tight
? now, you MUST check the mag timing with a synchronizer - you will be close but probably not close enough.

That said, if properly installed, mag gaskets rarely leak. I use DC-4

The RV's I've worked on thankfully offer much better access, so my response is probably moot. Ask any EZ driver if he'd rather change a mag or have a root canal

Thanks for all your responses

The gasket was indeed torn when we replaced it.

We did as the majority suggested, used the timing pin to hold the internal gear and replaced the gasket then retimed the mag

It took 10 mins longer to removed the rear cap and install the pin, still 10 mins is 10 mins!

My question was based less on the time issue and more about trying to understand the inner workings of the mag, such that the pin needs using even with minimal movement of the gear when replacing the gasket.