E: Engine A Washer Fell Out of My NEW ATD & How To Use My Light To Time The Mag

[CarlHungness]

I bought one of the new ATD's and upon unpacking it a tiny brass washer fell out on the bench. I I inspected the unit
and snapped it to and fro and all seemed to be fine. Thus I installed it, and this time I did it per the Lucas instruction sheets
whereby I was easily able to offer it up to the end of the magneto shaft, start the tubular bolt, and ultimately snug it up
in place. It has been 20 years since I've installed an ATD, have been using the B-TH. Somewhere along the line I came to believe
one should start the bolt to get the unit in position, put a socket over the center bolt and give it a slight rap with a hammer.
Each time I did so, I'd lock up the ears. This time, per instructions, it went on easily using the bolt.
Nevertheless, I failed to start the bike as reported in one of my other posts.
I removed the ATD and upon further inspection I noted the edge of a brass washer UNDER the piece of iron that holds
one of the return springs. It appeared to be a washer. I looked at the other side, and the washer was missing, it was lying
on my bench.
The washer appears to be held in by a stud that goes through the piece of steel that holds the return spring, and
upon assembly the assembler must not have had the washer centered.
So I've packed up the new ATD and returning it.
Since the timing cover was off and the mag still in place I thought I'd time it anyway, (with my bulb) and either await
another ATD or once again try my old one. In the past I have always removed the center bolt from the points holder, put in my alligator
clip turned the points holder until the Shoe J-U-S-T comes in contact with the first bump on the outer ring, and I know
pretty precisely where that is from prior experience, just past 6 o'clock. In fact an old pencil mark still exists there. Thus
the light goes on when I put the clip in the center hole..and goes off when the Shoe hits the bump, signalling the points
have J-U-S-T opened. I used that method multiple times to install the Lucas years back. I never had the points holder pop
out. Now a friend tells me I should definitely leave the bolt in so as not to disturb the points holder.
I've never used one of the magneto synchronizers which emits a buzz when the points just open, so I assumed my light
should do the same. I looked at "1951 Vincent Rapide Part 36 Ignition Timing" from The Mighty Garage on YouTube

and at the 17:00 mark the mechanic hooks up an alligator clip
to a cylinder fin, the other to the movable part of the points. He spins the plot until he gets the buzz, and says 'that's it,' the
points are just opening.
I thought I should be able to do the same with my dashboard light I've used for years. I have two wires soldered to the
light, one to the + battery, the other to the (removed) center bolt. Then I have one wire going from the - side of the battery
to ground (I've used the magneto end clip to hook it to). Thus I hooked up the negative wire to a head fin, and poked around
with the + wire on the point holder. I first tried the movable side of the points, light stayed on. No matter where I put the wire
the light stays on, with the points open or closed.
So where am I going wrong? I can't seem to 'break' the circuit to get the light to go off.
I believe Chris Lauders (spelling) noted I could insulate the center bolt and leave it in, but easier said than done.
Suggestions?

 

[bmetcalf]

The circuit is always complete, just through different windings. Per Magnetoman's recommendation, I use the L setting on an RLC meter (cheap enough on Ebay). It changes inductance by a factor of 10 when the points open.

 

[vibrac]

centre bolt insulation: Use a short piece of thin heat shrink tube on the taper

 

[lee_812d]

I've never taken this centre bolt out of the points holder, I thought you'd only need to do that if you are taking the holder off. The holder only goes on the magneto in one place (if I have this correct) there is a tag to locate it. So if it can turn freely that is not good (unless by turning it you are turning the whole shaft which will be possible if the ATD is loosened).

 

[CarlHungness]

centre bolt insulation: Use a short piece of thin heat shrink tube on the taper

Your suggestion is the only one I came up with too. Nevertheless, I am STILL trying to figure out why
one can hook up the magneto testing unit to one side of the points, the other to ground, and I can't
do the same with a small light as described in my post. In order to make the light go on-off the only
place I can hook it up to is the CENTER of the unit after I've taken the bolt out. Taking the bolt out
is a pain because the whole unit want to fall out on the ground.

 

[Chris Launders]

Carl, the circuit is from the moving contact of the points through the centre bolt, primary winding and to ground and the fixed contact, the tester will be comparing the resistance between the moving contact and ground directly (points closed) and through the primary winding (points open) and give a result based on this.
If you connect a battery and bulb across the points you will still get a circuit through the primary winding to the moving contact whether the points are open or not as either way there will be enough current flow to light the bulb, this is why we say you need to isolate the centre bolt (and therefore the primary winding, breaking that circuit)

 

[Chris Launders]

A quick sketch to show how the primary winding is connected, as you can see whether the points (A & B) are open or closed there is a circuit between them, all that varies is the resistance unless the centre bolt is isolated.

 

[oexing]

The resistance of the primary winding is close to zero, quite similar for any current going through the breaker contacts. This is why you cannot connect a bulb on the central bolt which is wired to the breaker. A buzzer may detect the difference between coil and breaker circuit and so timing devices are available from magneto specialists or in aviation business with their two mags that have to be timed exactly to fire at same degree, twin spark plug heads on these engines. Below a link to a simple timing set in UK, maybe you get an aviation set in USA at almost same price, nicer instrument anyway.
But when you keep undoing the central screw you may place a big plastic washer under the head of an extra screw with same thread to hold the breaker plate onto the mag shaft ?

Vic
Mag timing set

mag timer light plus buzzer

 

[lee_812d]

OK, I can see now the reason for messing with the centre bolt. With an LCR meter you don't need to (not on my bike anyway).

 

[CarlHungness]

A quick sketch to show how the primary winding is connected, as you can see whether the points (A & B) are open or closed there is a circuit between them, all that varies is the resistance unless the centre bolt is isolated.

View attachment 59977

Trying to insulate, and then remove the insulation later on the center bolt is more work than I want to do.
I've always been successful taking the center bolt out and am continuing to do so. A fellow member got angry
with me as he said I had to leave it it and sent me photos of the mag testing box. Thus I was right all along. I can take the center bolt out, fiddle until my light goes on-off-on, etc. When I put a bolt into the place where the earth
brush goes, the action of me finger tightening the bolt plays havoc with the on-off on my light, but that means
I am within a tenth of a degree of where I want to be on timing, so I don't worry about it anymore. I can remove the
center bolt, time it, then put the center bolt back in to hold the point holder. Thanks for the explanation.