A10 points replacement

[AlaskaJoe]

Hello all! I’ve removed my points in order to unsieze the cam ring. Now that it’s out, I figured I should replace the points as they are a bit worn. This is a ‘57 a10 super rocket with the k2f magneto. Two questions: is the correct part number 470609 for NOS Lucas points? Second, how do I remove the old points? I slid the retaining arm (see photo) but can’t figure how that arm comes off the plate. Does it just lift off? If so, what becomes of that little circle that the retaining arm rests on? Thanks to all for all advice!

[Billybream]

You have the original brass points assembly, try a good clean up, or source new old stock, as some modern replacements are poorly made.

[CheeserBeezer]

If you have been able to remove the cam ring cable connector (plunger as seen in photo), I suspect the cam ring is not seized.

[groily]

The pic here might help. (Ignore the funny green thing - that's a capacitor).
Note small screws retaining the spring blades, one longer than t'other. Note also the small buffer spring that (normally) should live under the two full length blades. The central fixed point is removed by undoing the screw on its outboard end. Watch out for damaged insulators, they are important. The funny green thing is used instead of an insulator - so you should have an insulator that isn't pictured between the fixed point block and the backplate.
The opening point is to earth, the fixed one is live (connected directly to the low tension or primary winding of the magneto by the central screw that you have extracted already).
The pimple under the retaining clip for the opening point is not an insulator, it just helps register the clip over the points pivot post.
If the camring is still stuck, then the plunger that operates it was probably out of position to start with, because it only comes out in the normal way when the camring is partially extracted from the housing. But if its mushroom head or the V notch with which it engages is very worn, a plunger can self-detach.
Best of luck!

[AlaskaJoe]

Thanks all! Yes, the plunger is out, but only did so after slow and careful extraction of the cam ring. That baby was stuck! As pertains to the points, I just wanted to replace the contacts as the ones in their are a bit discolored and seems the surface of them is worn a bit uneven. The bike did spark though, so perhaps I’m being over zealous? I just figured since I had it all apart why not freshen up. It was the movable arm of the two points contacts which I was unsure about how to remove or what Lucas part number it is  for NOS. Thanks!

[RichardL]

Contrary to what Groily said, don’t ignore the L-shaped green thing. He’s just being humble or modest because he was on the team that invented that “EasyCap.” You should get one, put it in and do the necessary minor modification in the mag armature while you have it all apart now and it’s easy. Almost certain spark will be improved. Check out the info at brightsparkmagnetos.com. Also, I wouldn’t shortcut on cleaning up the points unit as thoroughly as possible, replacing the points and any other questionable bits. It’s the brass block (and maybe the springs) that is hard to replace and quite worth keeping. The little button that fits in the hole in the top of the points arm is also hard to find new, but you can make one (as I previously described).

Richard L.

[Swarfcut]

One weakness of an old magneto is failure of the capacitor that (just as on a conventional coil and points system) is wired across the points. The Lucas design puts this within the armature and failure means a major strip down to the bare bones. You could say the whole bike is built around this troublesome component.

The Easycap is a modern, reliable, externally mounted and easily fitted answer to this problem. It does require a bit of simple surgery to isolate the original capacitor but the benefit of improved reliability and continued use of an otherwise working magneto is a small price to pay. A failing capacitor usually sparks fine when cold, but miss-fires and won't when hot, then works fine when it cools. Then just when you need it most.... It does nothing.


Mr G is indeed being modest......

Swarfy.

Additional. Apart from servicing points, pick ups and earthing brush anything else means the magneto must be removed from the bike and this entails a fair amount of work. I'd clean and reset the original parts and give it a go in the short term.

[groily]

As the Byrds sang  . .  there is 'A Time to Every Purpose'.
A 'time to promote and a time to stay silent', they might have said - but didn't.

I wasn't wanting to divert into a capacitor thread. The pic I posted was the best I had of an exploded view of the brass Lucas cb assembly, showing the bits AlaskaJoe was asking about.
But thanks muchly for your kind words Richard L and Swarfy.

Usual disclaimer though: a replacement capacitor will not solve other problems!

[AlaskaJoe]

I was curious about that green bit in a couple photos, I’ll do some homework on it for sure. This forum is just brilliant, and you lot have been very welcoming to a new BSA enthusiast who’s learning from scratch. Cheers!

[Slymo]

Magneto points degrade much slower than battery and coil ones. You'll likely find that a gentle dressing with a fine file and a polish on a stone or buff will have them working again for years.