D3000 mag manual

[Wingover]

Trying to find the info on setting timing on the dual mag.  There are a few letter like "L" in the top hole of the mag and the side hole that shows the red mark on the gear teeth.  I am reading the it should be the letter "K" on top but can't verify.

Does anyone have any pictures/instructions and what letter should be aligned on the top hole when the 25 degree mark on the back of starter ring is lined up with the top of the engine case halves while the #1 is on the compression stroke?

[N201MKTurbo]

If you look on line, you can find the service manual that explains it all.

The letters you are talking about are used to set the internal timing. To time the mag to the engine, take the plug on the end of the mag off and look in and turn the mag till the impulse coupling snaps than back it off till the red tooth is showing. That is where it should be with cylinder 1 is at 25 deg btdc. 
 

It won’t want to stay in that position, so you might have to move the prop a bit to get it on. I always put the gear with the cushions in the engine and then slide the mag into it. If it won’t time, then remove the mag and move the gear a tooth to get it right, then put the mag back on.

Just put the hold downs on finger tight with no washers till you get the timing right, then remove one nut and add the washers and make them finger tight and do the other nut. Set the timing precisely and torque the nuts.

[EricJ]

You shouldn't need to use the top hole for timing.   Move the #1 cyl to TDC, making sure the impulse coupler snaps.   You can double check that the red tooth is visible in the side hole, but that isn't usually necessary once it's been installed.  Then just use a mag timer connected to the p-leads to adjust timing.   There's a 25 degree mark on the back of the flywheel, along with TDC, etc., and that mark can be used to set timing.   Alternately there's a marked tooth on the flywheel that can be aligned with a marker on the starter.   I use the flywheel timing marks, and you can use a little laser pointer to align the shadow of the boss on one side of the top of the crankcase split to the 25 degree mark on the flywheel.   Otherwise you can line it up visually with a mirror or something.   

[N201MKTurbo]

20 minutes ago, EricJ said:

You shouldn't need to use the top hole for timing.   Move the #1 cyl to TDC, making sure the impulse coupler snaps.   You can double check that the red tooth is visible in the side hole, but that isn't usually necessary once it's been installed.  Then just use a mag timer connected to the p-leads to adjust timing.   There's a 25 degree mark on the back of the flywheel, along with TDC, etc., and that mark can be used to set timing.   Alternately there's a marked tooth on the flywheel that can be aligned with a marker on the starter.   I use the flywheel timing marks, and you can use a little laser pointer to align the shadow of the boss on one side of the top of the crankcase split to the 25 degree mark on the flywheel.   Otherwise you can line it up visually with a mirror or something.   

If you draw a line down the center of your inspection mirror, you can get the line aligned with the crankcase split and see where the line is on flywheel. 
 

For my Lycoming, I have a hack saw blade that is perfectly bent with the end cut off square. I tape it to the top of the case. It rests perfectly against a raised boss on one side of the case. It makes a perfect pointer.

[PT20J]

Another option https://www.aircraftspruce.com/catalog/topages/pointers.php

 

[N201MKTurbo]

54 minutes ago, PT20J said:

Another option https://www.aircraftspruce.com/catalog/topages/pointers.php

 

I sure it works almost as well as my hacksaw blade. And costs $67 more.

[EricJ]

Yeah, you just need a way to make it easy to align the case seam with the flywheel marks.   Mirror, laser pointer, hacksaw blade, string, ...there are probably a zillion ways to do it.
 

[Wingover]

Thanks everyone for the replies.  I was more curious as to what the letters are on the top hole.  I tried looking for the manual online but the ones I found do not talk about that.  
 

I understand that the same mag can be set internally for the 20 or 25 engines.

[N201MKTurbo]

3 minutes ago, Wingover said:

Thanks everyone for the replies.  I was more curious as to what the letters are on the top hole.  I tried looking for the manual online but the ones I found do not talk about that.  
 

I understand that the same mag can be set internally for the 20 or 25 engines.

The internal timing sets the E-Gap. The mag doesn’t care how it is timed to the engine. The only  thing that matters is the impulse coupling. I don’t think you can change the clocking of the coupling. AFAIK they only make 25 degree impulse couplings for that mag.

[N201MKTurbo]

http://www.aeroelectric.com/Mfgr_Data/Magnetos/Continental_Motors/X42003_D-2000_D3000_SM.pdf
 

see page 88

[N201MKTurbo]

In paragraph 9-2.8.11 it talks about mags with retard breakers and how to adjust the retard points. We don’t have those.

[Wingover]

7 minutes ago, N201MKTurbo said:

In paragraph 9-2.8.11 it talks about mags with retard breakers and how to adjust the retard points. We don’t have those.

Thank you for that and the link. It’s what I was after.

[N201MKTurbo]

FWIW, I have never removed the cam, but the point gap is allowed to be 0.012 to 0.020. I think you are better off closer to the 0.020. I adjust the two point gaps so they both open exactly at the E-Gap and at the same time. Then I check that the gaps are within the range.

You can only get them to open perfectly synchronized on one side of the cam. The other side will be off by a degree or so, just because of the mechanical precision of the cam. 
 

After you precisely set your timing on cylinder 1, do something nobody does and check the timing on cylinder 3. It will be off by a couple of degrees because it is on the other side of the cam. This is a dual mag thing.

[OR75]

remove all the spark plugs 

set the #1 cylinder to 25 deg BTDC (confirm that the point location on the starter gear is at the right location)

the mag adaptor should look like this (see 1st picture)

put the K in the top window (it should look like the 2nd and 3rd picture)

I find it helpful to use the mag lock tool (not impossible to do without but the space is so confined that it will likely unlock without the tool)

https://www.aircraft-tool.com/detail?id=ML20

make sure the gasket is in place and does not fall, use new lock washers each time you remove the nuts (order a bunch before starting the job !), follow the manuals instructions, ...

[Wingover]

4 hours ago, OR75 said:

remove all the spark plugs 

set the #1 cylinder to 25 deg BTDC (confirm that the point location on the starter gear is at the right location)

the mag adaptor should look like this (see 1st picture)

put the K in the top window (it should look like the 2nd and 3rd picture)

I find it helpful to use the mag lock tool (not impossible to do without but the space is so confined that it will likely unlock without the tool)

https://www.aircraft-tool.com/detail?id=ML20

make sure the gasket is in place and does not fall, use new lock washers each time you remove the nuts (order a bunch before starting the job !), follow the manuals instructions, ...

Thank you.  When my engine is set (on the #1 ) at 25 BTDC with the flywheel and line between the two engine case halves the letter L (not K) is lined up with the mark on the top of the magneto and I can see the red line in the side hole.

[OR75]

7 hours ago, Wingover said:

Thank you.  When my engine is set (on the #1 ) at 25 BTDC with the flywheel and line between the two engine case halves the letter L (not K) is lined up with the mark on the top of the magneto and I can see the red line in the side hole.

I am not sure you can see the letter when the mag is attached 

what is the issue you are trying to solve ?

 

[cliffy]

There is one BIG rule with dual mags- Pay Attention!

NEVER AND I MEAN NEVER loosen a mag hold down nut with a star washer underneath without replacing the star washer for a new one!!

Dual mags (and others) have fallen off because of this very problem. 

Anytime a hold down nut has been tightened and then loosened for any reason- THE STAR WASHER MUST BE REPLACED WITH A BRAND NEW ONE.PERIOD!!!

End of sermon.

[jetdriven]

Yup.  I’ve seen two magnetos at air races that fell out of the case. The pilot adjusted the timing and then tightened it back down.   Luckily they were two separate mags, but still. 

[Wingover]

9 hours ago, OR75 said:

I am not sure you can see the letter when the mag is attached 

what is the issue you are trying to solve ?

 

Just educating myself to make sure I understand the process.  Used to gap the points and adjust car engine distributors so I have an understanding of the mechanism but new to aircraft magnetos.

[EricJ]

1 hour ago, Wingover said:

Just educating myself to make sure I understand the process.  Used to gap the points and adjust car engine distributors so I have an understanding of the mechanism but new to aircraft magnetos.

The letter on the magnet is relevant only to setting the internal e-gap which would have been done during manufacture or the last overhaul or IRAN.  That sets the relative position of the magnet's field for timing the current generation.   It does not set the spark timing.  It's not something to worry about in the field, and can't be adjusted without removing the magneto and disassembling it.    The overhaul manual linked previously describes the process if you want to understand it.