Manual advance system

[AlaskaJoe]

Progress report. The ring is out! Using a pick to slowly work it out was an excellent tip! All is out and no damage. The groove in the mag housing seems a little rough, but honestly looks like it was machined like that originally. Next question, do you all recommend using grease or anti-seize when putting this all back together? Any reassembly tips or tricks to align the plunger to the groove on the ring? Thanks all! Pics for progress 😎

[Joolstacho]

I'd use a VERY light smear of oil on both sliding surfaces around that steel ring.
(Oooh and an hour or two meticulously cleaning those components wouldn't go astray).

[Swarfcut]

The square section groove in the housing holds a felt pad to retain lubricant and keep things sliding smoothly. There is matching hole in the cam ring to allow replenishment from time to time, this is also intended to lubricate the fibre heel against the cam ring. Also lubricate the moving points pivot pin.

Swarfy.

[AlaskaJoe]

The square section groove in the housing holds a felt pad to retain lubricant and keep things sliding smoothly. There is matching hole in the cam ring to allow replenishment from time to time, this is also intended to lubricate the fibre heel against the cam ring. Also lubricate the moving points pivot pin.

Swarfy.

Well, this felt pad was missing when I disassembled, I reckon it wore out ages ago. Is that something I can make or repurpose from another bike? I doubt I can buy it, but if so does anyone have a link or a part number?

[groily]

To put it back together insert the plunger in the housing so the mushroom head is about half-way down the fenestrated bit inside the housing. It will then align with its notch while the BIG notch will slip over the peg that limits camring movement. There's a fair bit of wiggle-room and it's usually easy. In some cases it's wise to hook the plunger to the cable first, in case space is tight.

However, with this one I'd pay particular attention to make sure that at each end of the arc of movement of the ring the plunger can't disengage when you operate the cable to full extent either way. Normally, the notch for the plunger is a V shaped one, and a snug fit over the mushroom foot of the thing. Not quite sure from the pic what form yours takes but I'm thinking the camring has been in the wars over the years. Many of them have.

Worth checking too, when you have the camring, plunger and cable all hooked up, that the camring can't chatter at full advance. Ie that when the plunger is fully down in terms of cable movement, the ring is firmly against its stop. You don't want the ring to have more movement available than the range of the plunger.

As far as a bit of felt goes - something from an upholsterer's offcuts or whatever will do. A slivver cut with a scalpel, and that's sorted. You can even make a pimple of the stuff to ram in the hole in the camring if you like - this'll transfer a tiny amount of the grease on the strip through to lubricate the heel of the opening point.

[AlaskaJoe]

To put it back together insert the plunger in the housing so the mushroom head is about half-way down the fenestrated bit inside the housing. It will then align with its notch while the BIG notch will slip over the peg that limits camring movement. There's a fair bit of wiggle-room and it's usually easy. In some cases it's wise to hook the plunger to the cable first, in case space is tight.

However, with this one I'd pay particular attention to make sure that at each end of the arc of movement of the ring the plunger can't disengage when you operate the cable to full extent either way. Normally, the notch for the plunger is a V shaped one, and a snug fit over the mushroom foot of the thing. Not quite sure from the pic what form yours takes but I'm thinking the camring has been in the wars over the years. Many of them have.

Worth checking too, when you have the camring, plunger and cable all hooked up, that the camring can't chatter at full advance. Ie that when the plunger is fully down in terms of cable movement, the ring is firmly against its stop. You don't want the ring to have more movement available than the range of the plunger.

As far as a bit of felt goes - something from an upholsterer's offcuts or whatever will do. A slivver cut with a scalpel, and that's sorted. You can even make a pimple of the stuff to ram in the hole in the camring if you like - this'll transfer a tiny amount of the grease on the strip through to lubricate the heel of the opening point.

Cheers Groily, this is a fantastic explanation. Just so I’m completely certain, my little square of felt sits in that groove under the cam ring? Pic attached. It seems kind of wild that it just sits there!

[groily]

Yup, the strip sits flush and grease-impregnated in the groove, and the camring keeps it there.
The felt also helps reduce chatter between ring and housing.
The points end cover should prevent in-and-out chatter, probably with the aid of a gasket.

[Swarfcut]

The end cover also carries the ignition cut out brush.  This bears on the rotating centre bolt, and by completing a circuit to earth  with the cut out switch bypasses the points and the engine stops.

I'm wondering if this bike came with a cover.... Those bolts securing the end housing look well established.

There are three basic design of end cover.

"Bell Push" Alloy dome with centre push button. This is the early type.

Bakelite cover with side mounted retaining clip. Easy access to the points, found an early '50's bikes.

Alloy screw on type with serrated edge which engages with a spring steel retainer on the end  housing. Later type.
These latter pair have a connection to the handlebar cut out switch.

Magneto identity plate carries a month and year of manufacture. Long number identifies the actual build specification, down to the smallest screw, such was the Lucas way to keep track of numerous variations to a basic unit.

Swarfy.

[Triton Thrasher]

Well, this felt pad was missing when I disassembled, I reckon it wore out ages ago. Is that something I can make or repurpose from another bike? I doubt I can buy it, but if so does anyone have a link or a part number?

I packed the groove in the housing and the hole in the cam ring with snippings of felt and dripped oil into it, not grease.

[AlaskaJoe]

Yup, the strip sits flush and grease-impregnated in the groove, and the camring keeps it there.
The felt also helps reduce chatter between ring and housing.
The points end cover should prevent in-and-out chatter, probably with the aid of a gasket.

Very helpful, thanks! One last question, how long should that piece of felt be? Should it be half the length of that groove or much shorter?

[groily]

I cut them to fill the groove, no reason not to.
Originals were full length and width, flush, and retained a useful dob of grease (or oil for them as prefers).
I normally add a fresh dob when doing regular maintenance of contact breaker and camring (every two or three thousand miles probably) and wipe an oily rag round the whole camring while I'm there. Also, I clean and grease the plunger in its 'ole - moisture can get in even with a decent rubber sleeve over the cable adjuster.

[AlaskaJoe]

The end cover also carries the ignition cut out brush.  This bears on the rotating centre bolt, and by completing a circuit to earth  with the cut out switch bypasses the points and the engine stops.

I'm wondering if this bike came with a cover.... Those bolts securing the end housing look well established.

There are three basic design of end cover.

"Bell Push" Alloy dome with centre push button. This is the early type.

Bakelite cover with side mounted retaining clip. Easy access to the points, found an early '50's bikes.

Alloy screw on type with serrated edge which engages with a spring steel retainer on the end  housing. Later type.
These latter pair have a connection to the handlebar cut out switch.

Magneto identity plate carries a month and year of manufacture. Long number identifies the actual build specification, down to the smallest screw, such was the Lucas way to keep track of numerous variations to a basic unit.

Swarfy.

I’m glad you brought this up, Swarfy, as it was one of my next questions. I do have the cap for this which is held in place by a moveable arm as seen in the pics below. What isn’t immediately clear to me, is how the kill switch wiring attaches to the metal bit inside this cap (other pic). Is there a special kind of wire end connector to this that presses on? The prior owner included a new Lucas harness so I’m rewiring the lot.

[groily]

Is there a special kind of wire end connector to this that presses on? The prior owner included a new Lucas harness so I’m rewiring the lot.

Feed a bit of wire through the 'acorn' nut that screws into the cover, put a washer over the bared end and splay the strands back against the washer - solder it if you like - and screw the acorn nut back in to retain it. The little split brass washers commonly used to secure HT cables to the magneto pick-ups are the normal thing, as they have a suitably small hole.

If rewiring the machine completely, it's the time to be thinking about your options. 12v or 6v? Electronic regulator? Earth polarity?
Loads of threads on here, and plenty of opinions and preferences, some strongly held! You're spoilt for choice, but some of them are a lot better than others  . . .

[AlaskaJoe]

Progress report! The cam ring is reinstalled with a nice slice of oiled felt in the groove, and with plunger hooked back up to cable I’ve confirmed it is moving as required when the lever is moved. This feels like a great step closer to running!

Follow up question since I’m still learning about this system. I’m struggling to understand how the movement of the cam ring changes the time A/R, since the points plate itself is fixed in the mag. When I retard the timing via the lever and the cam ring moves, how does that actually change the timing? Does that really change at what point before tdc the points open?

Thanks in advance (no pun intended) for the knowledge 😎

[groily]

When I retard the timing via the lever and the cam ring moves, how does that actually change the timing? Does that really change at what point before tdc the points open?

It does, yes. The points plate is fixed in position relative to the crank and pistons via all the many bits in between. So if you move the cam you'll change when the points open relative to everything else.

If the cam was fixed and the points backplate was the movable bit as I think you expected, the result would be the same. That's basically what the often-mentioned ATD  or ATU (automatic timing device /unit) found on the driven end of the magneto on probably the majority of these machines does - it moves the magneto armature and points plate relative to the crank and pistons, according to engine speed, while the cam is held in a fixed position.
All very "rub your guts and pat your head at the same time", but you'll get used to it!