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Installing mags

LettersFromFlyoverCountry

Well Known Member
I'm learning -- very, very slowly -- the ins and outs of magnetos. As you know if you've followed another thread, I had an RPM problem on the TMX IO-360 and it was suggested that the mag timing was off.

A pal, using the buzz box, set the mag timing, but when we tried to fire it up on Wednesday night, the prop whirred a time or two, then hung up briefly -- apparently this is a sign of a kickback about to happen. I had whirred it a few times with the mag off with no problem.

So, it was suggested, the mag needed to be internally timed. The mag was off the engine once -- when I was trying to get access to put the AN fitting on the oil port for the cooler lines -- and I probably wasn't very careful putting it back on ... or at least as careful as I needed to be.

What's odd is that I don't remember this occurring on first start last September and it only seems to have been a problem in the few times I've started the engine this spring. (It sat all winter)

Anyway, I took the mag off yesterday and took the distributor cap off and played around a little bit. I don't have a timing pin -- I've ordered one -- but just using an LP-4 pop rivet, I turned the rotor until it dropped in. This is the orientation if got on the impulse coupling assembly. It does not appear to be anywhere near the point at which the impulse coupling begins to wind and I was under the assumption that the timing pin assures that it is.

2012-05-12_17-10-16_581.jpg


Another question: I notice in this excellent article it says that the mag should be reinstalled like so:

First, remove the top spark plugs from all of the cylinders. Then, turn the propeller in the normal direction of rotation with your thumb over the spark plug hole on the No. 1 cylinder. When the air pressure on the No. 1 cylinder starts to build up and tries to blow your thumb off the hole, slowly continue to turn the prop until the timing mark listed on the engine data plate lines up exactly with the split line on the top of the crankcase for Lycoming engines or the split line on the bottom of the crankcase for Continental engines. Typically, Lycoming engine timing marks are located on the starter ring gear and Continental engine timing marks are located on the propeller flange.

I've been led to believe the proper spot is when the 25 degree mark on the flange is lined up with the reference hole on the starter. Which is it?

Any additional education you can contribute would be most appreciated.
 
Bob, the pin doesn't index at the beginning of wind-up. It indexes at point break. The case seam reference is used on some airplanes with a one-piece nosebowl. In this situation the timing marks are on the aft side of the flywheel. Timing marks on the front side are to be lined up with the index hole on the outer side of the starter housing. I've seen the instructions you just referenced before. They are generic and not very accurate. On your last thread I did a full rant about timing. Did I waste my time?
 
Yeah, so far. If the pin is really in the hole (pop rivet is fine)and your prop is at 25 BTC, then the mag should fit in its normal postion. The only way it won't is if the mag drive gear is indexed wrong inside the accessory case. Not likely unless it got pulled out and turned. Follow my last diatribe word for word. When all is done, you should be able to back up to engage the coupling, then come forward through TDC. Your coupling should snap at TDC or a bit after center, depending on the lag angle stamped on the mag label. If it does snap in that area, then you MUST be in the ballpark to the point where you can "fine time" it. Also, if it does snap in the right area, there is no way your left mag can be causing kickback even if its off a few degrees. If you still think your getting kicked back it would have to be caused by an advanced spark from the right. That would mean the right isn't getting grounded during start. You might want to time up that left one and hard wire the right (P-mag?) so you know its turned off and start on just the left. Eliminates possibility of the P-mag being whacko.
 
Question for you Bob. Are you using a key switch to start or individual toggles with a startbutton/toggle?
 
I have a toggle switch for the left mag and a toggle switch for the right lightspeed and a starter pushbutton.

I haven't tried starting the engine using just the Lightspeed b/c there was a warning against doing so that came with the engine. From what someone -- I think Mahlon -- said, whatever was in the innards of the Lightspeed that might've contributed to kickback by doing so (that was the warning) has been corrected but I haven't worked up the courage yet to try it.
 
timing

Just to clarify a detail: the way you have the mag in the picture, hold the mag in you left hand, rotate the gear counterclockwise until the impulse snaps. The rotate CLOCKWISE slowly until the pin drops in. Finding top dead center on cylinder #1(right front) is critical to mag timing. Then turn the prop backwards slightly past the 25 degree mark, then forward again to line up the mark. The backwards and then forward is simply to take out the error from the play in the gears.
 
I always start on the lightspeed. I hit the starter for a couple of revolutions and then turn on the light speed. Seems to work good for me. I have the plasma on the top plugs and the mag on the bottom. The Plasma just seems to start easier. Spinning it up helps to avoid the kickback. I toasted a Skytec starter with what might have been kickback. The casting failed.
 
I mentioned in the other thread that when I was running on both a couple of weeks ago and turned the mag off, the RPM went up. That's when the alarm bells went off.

Your set up sounds identical to mine.
 
Klaus talks about a mag check with a Plasma. Bottom line, you are comparing apples to oranges and the normal rules do not apply.
When I turn off the mag, I see a drop in RPM of not more than 10-20 rpm. When I turn off the plasma, I am seeing 125-150 drop. However, the engine continues to run smoothly which is the new go-no go point. I would think if the drop approached 175 rpm drop I would need to do some investigating. Basically, if anything changes from the norm, I might have a problem.
 
Separately, I'm hearing that I should not reinstall the mag on the engine with the impulse coupling in the orientation as above.

I think long-distance troubleshooting is not working; Tom Berge's going to come over this afternoon and give it a professional assessment.There are things firewall forward that I'm not yet able to conquer.
 
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The amazing Tom Berge was by today and he had that up on the iPad so, yeah, it actually was a big help.

We timed the mag as redirected and reinstalled, then timed it with the buzz box and all was looking good, so we reinstalled the distributor cap and hooked everything up and took it out to start it. No luck.

I must've flood on start (Mattituck says: Full mix, full throttle, boost bump, close mix, close throttle, boost pump off, throttle open 1/4, start)

It wouldn't catch and fuel started pouring into the FAB.

I removed the FAB and we tried again and no luck. Tried on the Lightspeed and is started right up and ran fine.

We too, the distributor cap off b/c we thought maybe we put it back on wrong but it's indexed via the screws. Reattached. Retired, nothing.

We then tried on the EI. Nothing. Lots of backfiring etc. And again, a fair amount of fuel pouring out of the servo as soon as the mixture goes forward.

So at this point I've got a name of a mechanic on the field and we'll just see how much more money I can throw at it before it starts.

I am ordering a "I Stumped Tom Berge" bumper sticker or T-shirt, though, because there are not many people on Planet RV who have.
 
Now that I re-read this, it sounds like your mixture is not being completely cut off. If you were in idle cutoff, it should not have been flooded.
 
Now that I re-read this, it sounds like your mixture is not being completely cut off. If you were in idle cutoff, it should not have been flooded.

It got flooded originally -- it appears -- because the original start procedure has mixture full forward with boost pump. when it didn't initially start; I repeated.
 
I wish I was closer, I feel realy bad reading all this, and somewhat frightened at the same time.

If you ever get so tired of messing that you are ready to throw a hand grenade at it, load that thing in a truck and ship it to me, I would be happy to sort things out for you :D
 
Thanks, Walt. That's very generous. I'm going to drop a note to Mahlon and see if he has some guidance.

It does seem to me that this has been a deteriorating situation without anything significant changing. It started fine last September, started fine again this spring and then slowly the starts got more problematic with signs of near kickback on starting, finally culminating with that problem getting to full RPM a few weeks ago.

But nothing really changed in that time (other than repositioning the ring gear to a proper location and that's not when the problem started appearing anyway).

Dan Baier suggests a problem with the impulse coupling so we'll see what Mahlon thinks and then figure out what to do.

A hand grenade? Ha! When there was fuel pooling up underneath the engine today, I wasn't far away from accidentally lighting a match.
 
Bob,

Don't say stuff like that.... If you did have a fire, all your insurance needs is a statement like that to refuse to pay....
 
Well, yeah, that and proof. But even so, I'm not concerned. I refuse to let lawyers and insurance companies make me afraid of my own shadow. I'll take my chances. The day I'm too afraid to laugh and tell a joke is the day I'll set ME on fire. :*)
 
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hey.. that's not covered by your life insurance either :)

It's covered after the policy has been in force for two years (in MN, state laws differ).... but in any case cashing in on your own life insurance is a scam that seems to have at least one fatal flaw. :p
 
Here's what Mahlon says to do:

Put a paperclip in the n umber one tower of the mag with the end bent over so that it makes an electrode with a small gap to the mag housing. Manually turn the mag over by hand 4 times and see if the impulse snap on one of the four revolutions makes a spark to ground from the end of the paperclip.

If it doesn?t make a spark or doesn?t click you need another mag.

If it makes a spark do the following:

Check the mag rotation on the data plate of the mag. Get your timing pin and insert the pin into the hole that matches the rotation on the data plate of the mag. The mag rotation should be LH and you should be using the timing pin in the L hole. If you have been using the R hole, in the block, because the mag is in the rt. position, that is your problem. Juts reinstall the mag using the L hole and all will work well. If you have been using the L hole then

Turn the mag over slowly by hand until the timing pin will insert ALL THE WAY INTO the distributor block using the L hole

Set engine at 25 degrees BTDC with number one cylinder on compression stroke.

Install the mag, then remove the pin and time to 25 btdc.

Ground the plead terminal.

Carefully turn engine over by hand and until impulse clicks. Do this in a fashion that if the engine should fire you are clear of the prop. When the impulse clicks the engine should be at TDC by the marks on the flywheel. If the impulse click between 5 btdc and 5 after tdc the engine should start on the mag. Hook the ignition wires and p lead up and remove the temporary ground you installed earlier.

Confirm the ignition wires are routed to the proper cylinders. The ignition wire b nuts that screw onto the spark plugs are marked for each cylinder it goes to. Whether it says bottom or top means nothing. Just make sure it goes to the correct cylinder by number.

Try to start the engine.

If it kicks back, you need another mag. I fit doesn?t and starts normally you are all set.

Mahlon
 
I like your attitude on this Bob and ...

Well, yeah, that and proof. But even so, I'm not concerned. I refuse to let lawyers and insurance companies make me afraid of my own shadow. I'll take my chances. The day I'm too afraid to laugh and tell a joke is the day I'll set ME on fire. :*)

That is my view as well - maybe it's a Bob thing. The thing I really like about this thread is I can sense your growing knowledge and self assurance in the process. You are going to be a "GO TO" guy on mag problems before this is over and it is heart warming to witness.

Bob Axsom
 
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Well....mmmm... no pressure now, right? Truth be told: I still haven't got a clue what I'm doing. :p

I'm really not sure I want to see a spark this evening on this thing or not.
 
Update: Well, I did get a spark. Not sure what I wat to do here. It's basically a repeat of what we've done a few times now. Wondering if maybe it would be best to send it out and have the innards--points and such-- checked out.
 
If that is what you think should be done

You have to build your confidence in the knowledge of your situation. Even if it is a complete waste of time it will eliminate doubt in your own mind.

Bob Axsom
 
Solved!

Yahtzee!

We finally got it figured out.

The timing pin from AS arrived today so back to the problem I went. I had already determined yesterday -- using the paper clip method -- that the mag was generating a spark on the #1 tower. So I sparked it and then backed it back to insert the timing pin (I don't know if it made any difference but in previous insertions of the pin last Sunday, we didn't trip the the impulse coupling).

I had already used the the Rite System kit I bought a few weeks ago to find TDC and backed the prop back to 25 degrees TDC (all plugs removed), then carefully reinserted the magneto and clamped it down lightly. Then, using the buzz box, the amazing Brad Benson timed timed the mag. The amazing Brad Benson helped time it, and we reinstalled all plugs and reconnected the ignition wires (after determining that the #1 sparked via the ignition wires to eliminate them as a cause of our woes).

Mike Hilger, who had just done by transponder check, joined us and confirmed when pulling the prop through the that the impulse coupling was firing about where it was supposed to (TDC, I think) and we rolled it out and attempted to start it.

I tend to think flooding the engine on Sunday was a source of a lot of our problems so I returned to the Mattituck method and she started right up. No kickback.

I brought the Lightspeed online but with the plane wanting to move -- the brakes having not been broken in yet -- I didn't like the orientation of the plane relative to a nearby hangar so shut it down without checking RPM etc.

We straightened things out and I restarted on the mag and everything looked good. I brought the Lightspeed online and then killed the mag -- and the engine started to stop. ARE YOU FREAKIN' KIDDING ME?

Have I just exchanged one problem for another??? Criminy!

Multiple retries, resetting the circuit breaker. Nothing.

At Brad's ingenious suggestion. We took the Lightspeed ignition wires off and checked the phase. Now, we'd just this a couple of weeks ago and when we rocked the prop at TDC of the #1 cylinder, we got a nice spark arcing on the 1/2 coils.... and 180 degrees later, we got an arc on the 3/4 coils.

As we moved the prop to TDC on the #1 cylinder tonight, however, we got an arc -- on the cube for the 3/4 cylinders. What the heck? How could this be. We not only got a proper spark when we did this a couple of weeks ago, we actually started the engine on the electronic ignition. How could this be?

Answer? We don't know. But we just swapped the ignition wires on the lightspeed to the opposite cubes and it started up fine on the mag, the Lightspeed was brought on line the mag was taken offline and she kept on purring.

So now we were back to where we were when we first detected our problems a couple of weeks ago -- about to break in the brakes and check the static RPM.

I wasn't happy with how the brakes were working but -- surprise -- I taxied up to the ramp at KSGS at 1700 RPM dragging the brakes and they then started working fine.

I turned the plane around on the taxiway and then tested the other thing that we wanted to do when we started this process -- the RPM. I'd swapped out a larger throttle arm on the Precision Silverhawk with a 2" throttle arm. It worked beautifully.

Almost fully pulled back, it idled around 550 RPM. Then I gave it the gun on the taxiway and about halfway in (or so it seemed), I was at 2150-2200 RPM. I considered that good enough so I pulled power, taxied back to the hangar and shut it down. The #1 CHT was quite a bit higher than than the others -- something I hadn't noticed before -- but that's not something I'm going to worry about right now.

The thing is: I don't know EXACTLY what we did to solve this problem other than just start over again. It seemed to me there wasn't really anything we did that we hadn't done before, but maybe just starting over was the way to go.

Many thanks to Brad and Mike and Tom Berge for their help and you all -- especially aerhed, jrs14855, and Dan Baier for their patience advice.

I think we can go ahead and call the DAR now.
 
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