Oil leaking into Bendix SF4RN-8 mag
- Thread starter jesse
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jesse
Touchdown! Greaser!
Ended up running into more road blocks, busted something, etc..took me awhile to locate the right parts. I have two good mags assembled and enough parts to build a third for a spare.
I hung the right magneto on the engine today and got the timing set (which was a PITA). I'll install the left magneto tomorrow and we'll see if it runs...
I hung the right magneto on the engine today and got the timing set (which was a PITA). I'll install the left magneto tomorrow and we'll see if it runs...
It'll run. I guarantee it.
jesse
Touchdown! Greaser!
Well, got both mags on, timing checked three times, proceeded by me yanking on the prop about a hundred times before giving up. I've confirmed that there is spark. I'm thinking something isn't right with the firing order. Going to find the BTDC of each cylinder and verify each lead is firing at the right time.
I'm thinking I missed something simple, IE hooked the wrong plug wires to the wrong cylinder. Hoping to have it figured out in the morning. Pretty sure I'm getting really close.
Turns out you can feel the spark on the plug wires with your hand even if you're pulling the prop through slowly..so it shouldn't take long to get this figured out. Just going to check every wire at every position.
I'm thinking I missed something simple, IE hooked the wrong plug wires to the wrong cylinder. Hoping to have it figured out in the morning. Pretty sure I'm getting really close.
Turns out you can feel the spark on the plug wires with your hand even if you're pulling the prop through slowly..so it shouldn't take long to get this figured out. Just going to check every wire at every position.
It's easy to get things 180° out. Make sure you are timed to TDC Compression, not overlap. I just use my thumb on the plug hole to make sure.
jesse
Touchdown! Greaser!
Yeah. I considered the whole 180 degree issue but pretty sure that's not what I'm facing right now. I bought this setup: http://www.ritesystem.net
Either I have something incorrect in the magnetos or I have the spark plug wires totally messed up.
I confirmed the points are opening on both mags at the right #1 BTDC position.
Also when I find TDC with the RiteSystem it matches the TDC mark on the crank.
I've confirmed the #1 is firing at the right moment by locating the BTDC firing point, spinning a bit before that, then pulling the prop through with my hand holding the spark plug wire.
I haven't however checked every plug...which is where I"m going next. If that doesn't get it running then I pretty much have to have an issue with the magneto internals.. Hoping that's not it as I don't want to have to yank them off and put them back on again..it's a ***** because the firewall is so close to the mags.
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That's fine and dandy, but you still have to orient to the cam, and the crank mark comes around twice to the same "correct" position per correct cam time. Just sayin, that's the first thing to check to make sure you have right, physically check.
jesse
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Hmm. I'm thinking you've identified the problem. Idk why the **** I didn't think to ensure it was on the compression stroke. I'll check that first..then I'll check that the plug wires are all right.
I was thinking that it didn't matter as long as I found TDC, went the right number of degrees back, and ensured the points opened there with the right plug firing.
Wish there was a good animation of a four stroke aircraft engine and it's magnetos in motion so I could wrap my head around this better.
Same as the animation for a 4 stroke anything engine. The only thing about a Magneto vs a distributor is it generates it's own electricity. The mags are driven by a gear off the cam/crank.
Typically, if you are anything but 180° off in a spark order problem, it's going to cough, pop, and kick on you.
jesse
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Yeah. Nothing. Other than one little pop after maybe 50 pulls but there was no prop motion from it and it seemed like it came straight out the exhaust..So the exhaust valve must have been open and it must have just gotten lucky and lit a bit of something.
Yep, you're 180° out, swap the wires on the plugs and you're done.
jesse
Touchdown! Greaser!
Hm..Swap in which way? That'd sure be a **** of a lot easier than pulling the mags again like I was thinking I'd have to do.
If the firing order 1-4-3-2, you would swap 1<->3 and 4<->2, of course you can spin the harnesses 180° on the mag.
jesse
Touchdown! Greaser!
Hmm..It's 1-3-2-4 I think. Cont A75
I was thinking I'd swap the 1 and 3 and swap the 2 and 4. Based on looking at my spare mag right now it seems like that'd work.
If that is the order and you swap 1&3, whichever are next to each other on the ends, you are swapping 180° on the crank but only 90° on the crank and you will end up getting the prop to bark your fingers. Remember a crank cycle is 720°. The first two cylinders fire on the first 360° of crank or 180° of cam, and the second pair on the second 360° of crank or last 180° of cam.
Tom-D
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Tom-D
Does your distributor gear have a red tooth?
Did you align the distributor gear drive gear ?
Place your engine in firing position, on the #1 cylinder. place the Mag in the firing position for #1 cylinder.
mount the mag.
Use the time right to tweak the advance timing.
at firing position you should see the red tooth of the distributor gear. thru the inspection hole in the top of the mag housing.
Did you align the distributor gear drive gear ?
Place your engine in firing position, on the #1 cylinder. place the Mag in the firing position for #1 cylinder.
mount the mag.
Use the time right to tweak the advance timing.
at firing position you should see the red tooth of the distributor gear. thru the inspection hole in the top of the mag housing.
jesse
Touchdown! Greaser!
I did all that but it appears I set it on the exhaust and not the power stroke. Assuming that I did make that mistake...
If the firing order is 1 -3 - 2 - 4 -- how should I swap the plug wires to get it where it needs to be?
Tom-D
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Tom-D
Too bad you didn't simply replace this and leave the rest of it alone ..
http://www.ebay.com/itm/10-357592-1...6N-Magneto-Drive-Shaft-Oil-Seal-/131343030538
http://www.ebay.com/itm/10-357592-1...6N-Magneto-Drive-Shaft-Oil-Seal-/131343030538
jesse
Touchdown! Greaser!
I'm assuming the drive shaft for the magneto turns at the same rate that the crank does. Based on everything I can see about how this works that's true. If so it fires a plug every 180 degrees of rotation of the magneto drive shaft.
1 fires, drive shaft rotates 180 degrees
3 fires, drive shaft rotates 180 degrees
2 fires, drive shaft rotates 180 degrees
4 fires, drive shaft rotates, cycle repeats.
It takes 720 degrees of rotation of the magneto drive shaft to fire all the plugs.
I can't sort out in my head why swapping 1 and 3 and 2 and 4 wouldn't get me where I need to be. I have a spare mag torn down right now that I'm looking at....
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jesse
Touchdown! Greaser!
I don't see how that would make any difference with my current issue. You can't replace that without pulling the mags and removing the front plate of the mag. You'd still have to reinstall the mags and if I made the same mistake (50/50 chance) I'd be in the same shoes right now.
What actually started this mess was adjusting the timing, which ripped the flange gaskets on both mags creating a massive oil leak. They had to come off and while they were off I pulled the top cover and saw one was full of oil.
jesse
Touchdown! Greaser!
I'm going to get up at 5am and head to the airport and try to sort this out. First thing will be confirming whether or not I'm 180 degrees out. At that point, if I am, I'll evaluate the plug wire swap option versus pulling the mags and reinstalling.
Normally it takes 360 degrees of rotation on the magneto to fire all the cylinders.
Before you get too confused, make sure you can do it as a wire swap length wise. You may have to pop the mags and do a proper timing. If you can pull the wires at the mag/distributor end, that works best, just shift each wire across from where it is.
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Jessee,
Hire the handicapped. They are fun to watch.
Just raggin' on 'ya.
Hire the handicapped. They are fun to watch.
Just raggin' on 'ya.
jesse
Touchdown! Greaser!
Got it running, but my wiring harness is junk. When I swapped the wires on the mag end they basically fell apart. There was basically nothing left on at least four of the wires, probably failed completely when I pulled them out of the mag. I'm amazed it ran at all.
I have to leave town for a week for work and when I get back it'll be too cold to mess with. Will pickle it for now and replace all the spark plug wires in the spring.
Btw the spark plug wires are ridiculously expensive...need to find an experimental source.
Someday I'll have this thing in tip top shape. So far every minor issue I've chased has escalted into rebuilding whatever entire system it was a part of.
I have to leave town for a week for work and when I get back it'll be too cold to mess with. Will pickle it for now and replace all the spark plug wires in the spring.
Btw the spark plug wires are ridiculously expensive...need to find an experimental source.
Someday I'll have this thing in tip top shape. So far every minor issue I've chased has escalted into rebuilding whatever entire system it was a part of.
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I would not be surprised if you could build your own...
...very glad you found the issue with timing, and that in the process you found the wire issue. Best place to find it, and (call me nuts) we like our Jesse. In one piece. Breathing.
...very glad you found the issue with timing, and that in the process you found the wire issue. Best place to find it, and (call me nuts) we like our Jesse. In one piece. Breathing.
jesse
Touchdown! Greaser!
Actually, now that you mention it, earlier I was thinking what I really need is a bolt on electronic ignition system that also has a built in alternator. Such a thing does actually exist but the built in alternators only generate enough juice to pier the electronic ignition system. I want more amps, so I can make it IFR.
If only I were retired. This stuff is cake compared to the software I spent most of my time on.
jesse
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This looks like a good option for me and $160 is a hell of a lot more reasonable.
http://www.aircraftspruce.com/catalog/eppages/shieldedharness.php
bnt83
Final Approach
Any elbows or will straights fit?
jesse
Touchdown! Greaser!
There are elbows off each plug, and bumps in the cowl to permit that. These wires are straight, however, they claim that's a non issue since their wires are way more flexible. Whether or not that's true I guess I'll find out.
Tom-D
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Tom-D
The seal can be changed by pulling the gear, removing the seal with the proper seal removing tool, press in another and replace the gear. then simply flush the oil out of the mag.
timing the mag, is that the issue you have now.
Bill Watson
En-Route
Loving the old hardware and old school discussion. I had the chance to tear down my Slick mags for a SB - these old Bendix units are quite a bit more substantial and hefty.
Carry on, good luck!
Carry on, good luck!
jesse
Touchdown! Greaser!
The mags are internally timed correctly without a doubt. The issue was the engine being 180 degrees out of position when I mounted them which would have happened regardless.
Personally, I kind of want my mags to not **** out of me, and considering how I have no idea what condition they were in when they were assembled or when that was done I take the road of caution.
I ended up replacing quite a few parts in both. So I'm happy with my decision to inspect them.
jesse
Touchdown! Greaser!
Messed around with it some more today and have it running smooth as can be now. Mags checks out perfectly. Runs great at all power settings. Still a few things I'm going to want to do before I fly it.
For those that are curious, if you mount it 180 degrees off, for it to fire correctly you: Hook #1 cylinder up to #2 on the mag. #2 cylinder to #1 on the mag. #3 cylinder to #4 on the mag. #4 cylinder to #3 on the mag.
For those that are curious, if you mount it 180 degrees off, for it to fire correctly you: Hook #1 cylinder up to #2 on the mag. #2 cylinder to #1 on the mag. #3 cylinder to #4 on the mag. #4 cylinder to #3 on the mag.
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Let'sgoflying!
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Dang I had the audio turned off and thought it was cranking by itself!
Smoooth.
Smoooth.
Normally easier to just pull it and put it on right and re-time.
Bad form to put things together 180° out even if it does work fine.