K2F mag, points mounting plate

[Lannis]

Well, about 100 miles into its maiden US voyage, the Golden Flash said "Stop over here and Fix Me Now!", it was spittering and sputtering and missing and not running right.

Spun the points cover off, and some metal chaff came out.  I turned the engine over and couldn't see the points opening and closing, although the adjustment hadn't changed.

Took the points out, and it turns out that the pin upon which the movable points pivot, which fits into a hole in the brass mounting plate which keys onto the armature shaft, had wallowed out a big oval hole in said plate, and the points were moving all over the place.  When the cam bumped the follower that's supposed to open the points, the points just moved and didn't open.  In addition, the spring and the mounting screw for the spring had rubbed against the cam ring and worn themselves down (don't know if the cam ring was damaged or not, it's apparently pretty hard and wasn't scored).

So this wasn't fixable on the roadside.  Call out a truck and on to the rally in hopes of being able to "Overnight Ship" a new points set and points plate ($150 just for the parts, OI!) to the rally, but that didn't work, "Overnight" means "**** you, we'll get it there when it suits us", it's STILL not there.

So it looks like an obvious fix:  Slide the new points plate and points onto the keyed shaft (ignition timing should still be OK), and adjust the points gap.

Is there a carbon brush that goes into the points plate?   There looks like there's a place for one, but I must have lost mine on the side of the road?  Are there FOUR carbon brushes on this mag?  One for each pickup, one "earthing" brush, and one behind the points?  Are they all the same brush?

Thanks for any initial insight you can give me.  Anyone ever had this happen to them?  Wonder why it happened, there doesn't look to be that much force on that pivot?

Lannis

[groily]

Bad luck Lannis! The point pivot should be fast in the backplate (and vertical!) and yes there should be a brush on the back of the plate, plus a spring. Not sure if all the brushes are the same or not - but the earth brush can be used in an emergency as an HT brush and the mag will still work. I think a lot of the brass cb backplates are getting a bit past it these days. The pivots can get a bit worn and make the moving point wobble too much, but coming adrift at the base of the pillar is even worse. A steel plate is available from various people - SRM for one - and is far cheaper than the one that didn't get to you when your need was dire. Don't like them all that much myself, but they do work and you get 'car-type' adjustment, which is in some ways easier than grambling around with magneto spanners to do the locknut up on the fixed point in the standard arrangement.
Whatever you replace the broken item with, I'd tend to check the ignition timing, by the way. There can be quite a bit of difference with new points and/or a different cb backplate - enough to make it worth checking anyway, and possibly changing. It's all to do with the wear on the heel of the moving point, etc etc.

[shabashow]

When I fitted the carbon brush in the points cover, the brush diameter was slightly larger than that of the hole it was meant to go in, so a very light sanding got it to fit. I think this was because I broke the original brush and used a spare pick up brush. It still seems to work.
I got my points reconditioned by a firm called Classic Motorcycle Electical Services in Bristol, who advertised in the back of the BSAOC magazine, so you may want to keep your pieces and get them refurbished, for a spare.

John

[BSA500]

Another good supplier is Independant ignition in Devon?.I prefer the brass points plate because I went through 3 sets of the steel ones, pins kept coming loose (all three from different suppliers).I have damaged the brass keyway(my fault) but each time it was fixed by Independant for about a tenner.

[Triton Thrasher]

There's no brush in the points plate. There might be a cut-out brush in the cover over the points.

You have suffered a fault I've seen in several steel points plates. See here:

http://www.audioworld.net/BSA/forum/index.php?topic=1054.0  I expect it happens to everyone who tries to use them for high mileages.

You can fix it at the side of the road by peening the end of the loose pin.  Sometimes!

I'm experimenting with soldering the post in place. Interesting that Independent has the brass ones. Ta BSA500.

[fido]

There's no brush in the points plate. There might be a cut-out brush in the cover over the points.

Some points plates have an additional earthing brush at the back of the plate but it does not do much as long as the main earthing brush to the armature is functioning.

[Triton Thrasher]

There's no brush in the points plate. There might be a cut-out brush in the cover over the points.

Some points plates have an additional earthing brush at the back of the plate but it does not do much as long as the main earthing brush to the armature is functioning.

I thought that was just an alternative position for the earth brush, but there are definitely too many variations on Lucas magnetos for me to grasp.

[groily]

There are certainly brush and spring assemblies on some if not all K2F backplates, I've got a few of them here! With cut-out brushes bearing on the centre screw in some end covers, that makes a max of 5 bits of carbon by my reckoning.
It is amazing the number of detail differences between these things, but then the production run was long in years and must have numbered 100s of thousands. Remarkable things. Just as well that most bits are inter-changeable . . .

[Triton Thrasher]

Tony Cooper has just sent me a K2F points plate of a type has had made. It's certainly rivetted differently from my other failed ones. We'll see how it does.

[Triton Thrasher]

Hey Lannis!  Is this fixed yet?

[Lannis]

Hey Lannis!  Is this fixed yet?

I really apologize for not following up on this last year, people were very helpful with their suggestions and I owe it to them to say what eventually worked!

Yes, I put the new points plate in, and the bike fired right up.   We never did get it running at the rally we were going to, because "Overnight Shipping" on Friday at $33 for a tiny package means "Tuesday Delivery".

After a bit, the bike wouldn't shut off any more!   I ended up replacing the earthing brush, the magneto cap brush, and it would kill one cylinder when I pushed the button.   Finally replaced the button with a heavy-duty toggle switch and now she kills like a good 'un.

Rode the A10 to work today, she's doing very well so far, we'll see how she is in heavy traffic on the way home .... !

Lannis