Seeking Mag Synchronizer Help

Not using the timing marks on the ring gear, nor using one of those contraptions you attach to the spinner, is there an easy way to determine top dead center (for magneto timing)?

Also, silly question, but for my sanity, the left magneto is the one in front of the pilot seat, and the right mag is the one in front of the passenger seat, yes?

I can not get my mag synchronizer to work at all.....I feel certain its operator error.

Seek the help of an A&P or someone familiar with the process. The ignition has to be ON for this, aka mags hot.

Timing

The engine needs to be at 25 before TDC to time mags, assuming that's what the engine data tags says. Remove number one spark plug, turn over engine till it comes up to compression, you can carefully insert a screwdriver into to the spark plug hole and feel the piston move. Right at TDC you should hear the impulse coupler snap, this should be right at TDC. If you have a flywheel with 149 teeth, turn the prop backwards about 10.3 teeth, that should be 25 BTDC, but check my math. 360 degrees 149 teeth is 2.416 degrees per tooth. 25 degrees divided by 2.416 Is 10.34. But you need to know when the points move, so you really need the sync box. The two biggest errors are switch not on both and impulse coupler not snapped. The right left is as you are sitting in cockpit looking forward.
The left mag is usually the impluse.

Correct on the mag location I.D. Here is how to get very close to finding TDC without the ring gear or a dial gauge:

Leave ignition OFF
Remove all spark plug leads and all the top plugs. It’s now safe to rotate the prop.
Stick your thumb in the top empty spark plug hole of cylinder #1.
With your thumb firmly in hole and rotate the prop in direction of regular travel until you feel air blow by. You are now in the compression stroke of #1. Stick a 1/4” wood dowell in the #1 hole and hold pressure on it on top of the piston.
Continue rotation and you will come to a point where the dowell rod stops coming up and starts to go back down. You can rock the prop back and forth to get really close. Keep gear lash I’m mind as you need to stop the rotation when turning in the correct rotation, not going backwards. You can now install the ring gear to identify exact TDC using the TDC mark on the forward face of the ring gear with the .062” hole on the front of the starter, or use the aft TDC mark on the ring gear lined up with the case split.

Follow the directions that came with your magneto buzz box. With the plugs removed, there is no danger of an accidental start from rotating the prop and you do need the ignition turned ON to time it. If your still having problems with the buzz box not working and the internal battery is good along with correct lead locations, remove your p-leads and try again. Sometimes there may be a problem with them or the switch itself. Good luck!

blueflyer said:

Not using the timing marks on the ring gear, nor using one of those contraptions you attach to the spinner, is there an easy way to determine top dead center (for magneto timing)?

Also, silly question, but for my sanity, the left magneto is the one in front of the pilot seat, and the right mag is the one in front of the passenger seat, yes?

I can not get my mag synchronizer to work at all.....I feel certain its operator error.

Click to expand...

This.... http://www.aircraftspruce.com/catalog/topages/timing_ind2.php?clickkey=3240965 IS the easiest way to find the TDC of your motor. The timing marks on the flywheel to the case are vague at best.

Get the proper tools and learn the proper procedures. Timing is very important......... Good luck.

Thanks for all the replies. I believe I am doing what everyone has described, although I may try the wooden dowel to feel TDC.

My mags are on ( toggle switches) and I find compression stroke of #1, impulse coupler pops, turn the prop backwards a little, and I walk around to the the ring gear, its right at the appropriate mark against the case. When I turn on my buzz box, I get nothing...I try and move the prop just a little in either direction and I still cant get a peep out of my buzz box.

It buzzes like crazy when I unhook one of the buzz box P-lead connectors from one of the mags, so I know my battery is good in the buzz box.

My A&P is coming today to complete my CI, but I thought I would try and time the mags before his arrival.

wires

Only thing I might add to the already great replies is:
Check that you are indeed attaching the buzz box leads to the P-Lead terminal and not the ground terminal, as they are right next to each other and I always have to check myself when I am attaching mine.

Already said above but worth repeating:
Buzz box black lead to good ground.
Ignition/mags hot/on.
Another easily done problem is timing to TDC instead of 25 degrees.
No need to ask how I know about these issues

blueflyer said:

Thanks for all the replies. I believe I am doing what everyone has described, although I may try the wooden dowel to feel TDC.

My mags are on ( toggle switches) and I find compression stroke of #1, impulse coupler pops, turn the prop backwards a little, and I walk around to the the ring gear, its right at the appropriate mark against the case. When I turn on my buzz box, I get nothing...I try and move the prop just a little in either direction and I still cant get a peep out of my buzz box.

It buzzes like crazy when I unhook one of the buzz box P-lead connectors from one of the mags, so I know my battery is good in the buzz box.

My A&P is coming today to complete my CI, but I thought I would try and time the mags before his arrival.

Click to expand...

The buzz box should be buzzing at 25* BTDC, not TDC, which is where it seems like you are expecting it to. Are you turning the prop back far enough to check?

Chris

You could be right, I may not be turning it backwards far enough. I'll know this afternoon once the mechanic arrives.

Feeling with a probe is OK for getting close (like a couple degrees), but to know with any required precision a piston stop is required. Marks can be off, a piston stop is the only way to be sure.

It does not have to be done each time unless there are no other references (for timing or TDC) when calibrating/setting the spinner hat.

To reemphasize you must go past TDC to release the impulse coupler, this should happen at TDC, where you will see the TDC mark on the back side of the gear support line up with the case parting line. You will also note the crankshaft turns very easy back and forth 2~3 degrees at this position. Thats close enough for our purpose. Then rotate the prop BACKWARDS to about 40~50 degrees BTDC, then rotate in normal direction of rotation and come up slowly on your timing marks, 20 or 25 as required, indexed at the small hole in the starter as you monitor your buzz box. If you need to adjust, repeat the procedure before checking it again.
You don't need any wooden sticks, piston stops or index wheels to do this unless you feel the need to verify the factory timing marks.
Tim Andres

BillL said:

Feeling with a probe is OK for getting close (like a couple degrees), but to know with any required precision a piston stop is required. Marks can be off, a piston stop is the only way to be sure.

It does not have to be done each time unless there are no other references (for timing or TDC) when calibrating/setting the spinner hat.

Click to expand...

Plus one. I will not time my engines with the timing marks any longer as both of my machines where off. On the IO-360, about a degree. On the 0-320, a bit more than two degrees. This made more difference than I expected in my CHT's.

It helps SO much to have the buzz box attached to the P leads on the mag and not on the ground post.