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Mag timing - alignment

Drippy

Well Known Member
Guys,

OK here is my latest question. So I went to time my right mag and can't get it to the proper spot. As I try to rotate the mag to the left CCW as part of the timing process the mag hits the attachment foot. I chamfered the foot but still need to go a bit further.
https://photos.google.com/share/AF1...?key=bW41dmNWMWZrSUlsSGpsNmNWZmx2Y0RpSkVCOHVn

To be clear when I line up the red line to time the gears and have my prop at 25 before TDC. The Bendix 1200 interferes with the top attachment lug which prevents it from rotating enough to properly time.

Is there anyway to change the timing verse the mag body alignment?

Thanks Drippy
40644
Going to the airport Monday!!!
 
timing

Use the timing light to locate where the points start to open. I use on of the locking devices. Just be very careful not to put any load on the gear with the locking device in place. Tighten the nuts finger tight, remove the locking device, and fine tune the timing with the timing light.
Timing light is not exactly the proper terminology its the buzz box with three leads and two lights as well as audio tone.
 
thanks but not sure

Thanks but not exactly sure what you are suggesting, sorry I must be tired.

What does the second sentence mean? What locking device?
 
locking device

It is for Bendix mags, similar in theory to the timing pin for the Slicks. Holds the internal gear while you install the mag in the accessory case. Some people don't like them, they work fine if you don't put a lot of load on them. They screw into the hole where you see a portion of the plastic internal gear. Aircraft tool supply I think has them.
 
Thanks but not exactly sure what you are suggesting, sorry I must be tired.

What does the second sentence mean? What locking device?

He is thinking of Slicks which use a locking pin as part of the process. Bendix should have something similar.
This shouldn't't be happening. Go back to basics. Make sure the flywheel is correct (near TDC of #1), read the marking on the front at the tiny hole near the starter, or aft side reading at case split, set to 25 early. Make sure mag is set where it belongs on #1.
 
Sounds like the timing gear on the mag needs shifting one tooth . Hard to tell which direction but if it was a Slick the pin inserted in the correct hole would help you decide. Not current on Bendix procedure
 
Timing

He is thinking of Slicks which use a locking pin as part of the process. Bendix should have something similar.
This shouldn't't be happening. Go back to basics. Make sure the flywheel is correct (near TDC of #1), read the marking on the front at the tiny hole near the starter, or aft side reading at case split, set to 25 early. Make sure mag is set where it belongs on #1.
Not thinking of Slicks, I was very specific that this is a locking device for Bendix mags. What frequently happens, you start with the internal gear in the proper position and as you install the mag and mesh the drive gear into the accessory gear everything moves enough that you have an error that cannot be corrected by rotating the mag. You need to remove the mag and start over. Same principal as Slick pin but different device. Both the Slick pin and the Bendix locking device can damage the mag if you forget to remove them and turn the prop.
 
back to basics

OK I will give it another try. I have the flywheel at 25 but will double check I am on a compression stroke with cylinder #1. I pulled the plug and think I checked but after messing with this for a few hours am doubting myself.

Worst part is I am not far off 1/8'' or less of rotation once I remove the foot and it gives me that nice beep.

I sent a not to Mark at TropicAir parts he rebuilt the Mag for me and I am hugely impressed with this customer service hopefully he can help me again. I am sure he can walk me through shifting of the timing gear if required.

Thanks

Mike
 
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You have installed your mag one tooth off. Purchase th alignment tool or borrow it. Set your timing to TDC for number one cylinder, and install the mag with the tool inserted allowing for sufficient clearance to adjust the timing in the future. Do a search on u tube, there are many videos of this.....
 
Age

How old are the mags. It sounds like the internal timing points are so worn that it won't let you rotate enough. I think a mag overhaul might be in order

Gary Specketer
 
540 is different

For the 540, the mag "gear" is not physically attached to the mag, it's in the accessory housing. The mag interfaces with it via a pair of rubber cushion clamps and the magneto drive "coupling". I had the same problem with my right mag. I needed to pull the gear out of the accessory housing, and rotate it one tooth, then re-install it.
 
+ one for off by a tooth.

Just be glade they are not helical gears mashing up. Those take some time getting used to offsetting. Hope this helps. Yours, R.E.A. III #80888
 
Ron has it. You probably need to pull the gear out and rei-ndex one tooth. If you have this problem on the 4 cylinders where the gear is attached to the mag, you pull the gear and give it a 180. That swaps you half a tooth.
 
I'm thinking the mag should initially be set on the engine... with the timing pin locked in the mag....when #1 is at Top Dead Center (TDC). Give your magneto manufacturer a call for 100% assurance & accuracy on this. Then, when you time the mags, you use the timing light and the 25 (or whatever)degrees Before TDC.
 
Regular Mags are not installed with the #1 cylinder at TDC. They are installed with the engine at the point BTDC that is listed on the data plate. Pmags are a different story but we're not discussing those here. Several posts have been made that are giving the wrong information. The OP is actually using the proper engine position.
 
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do Bendix mag installations have the option of an impulse coupling like slick? If so be sure you're setting the timing with the impulse coupling already 'kicked " and out of the way . If no impulse arrangement Ignore this post.
 
May timing

Be sure when you are rotating the engine for timing to click the impulse then set your timing.
 
Check the E-Gap

Possibly check the E-Gap (aka internal timing or points to mag drive shaft timing), sometimes if its set to one end or the other of the permissible range, it is not possible get the mag to time to the engine within the adjustment range of the hold down slots. Not sure what the 1200 series E-Gap is, but the S-20 series was something like 8 to 14 deg. Setting the E-Gap to the mid range is optimum, but sometimes you have to set it towards one end or the other to account for tolerance stack up. The Bendix mags use special tools (dwell pointer and degree plate) and a timing light for doing this.
 
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