The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: t20racerman on 19.07. 2013 12:33

Title: Does points opening ramp lead or trail.....
Post by: t20racerman on 19.07. 2013 12:33
Hi all

Not been by for a while (sorry!) but I could do with some advice re points. Mine fell apart and I got some new ones, and they fell apart too! (Such quality!)

Anyway, I rummaged through my spares for a temporary fix and have two sets of points - but they are mirror images of each other. I'm pretty sure that the ones on the left are correct, and that the lovely old brass plate ones on the right are the wrong ones, but could somebody please confirm this for me.

Also, been trying to get a whole points unit as my backing plate is damaged/worn as well as the points themselves, and I can't seem to find a supplier. Clearly I haven't looked hard enough, but just thought I'd ask here before phoning around and surfing the net again.

Hope you are enjoying the sunshine!
All the best
Adrian
Title: Re: Does points opening ramp lead or trail.....
Post by: muskrat on 19.07. 2013 14:44
G'day Adrian.
The ones on the right are right, or do you mean the other left.lol
Cheers
Title: Re: Does points opening ramp lead or trail.....
Post by: t20racerman on 19.07. 2013 17:55
Hi Muskrat and thanks... but....

Are you sure?  I searched the forum about this after posting and found this thread - with lovely pictures of the points...

http://www.a7a10.net/forum/index.php/topic,67.msg175.html#msg175

These are the brass points, but are the same direction as the ones on the LEFT of my photo, not the right  ??

Adrian
Title: Re: Does points opening ramp lead or trail.....
Post by: muskrat on 19.07. 2013 21:18
Ah, I see my mistake. The ones on the right are for a magie spinning in the opposite direction (anti-clockwise looking at the points). The ones on the left spin in the right direction but are different to our K2F's.
Sorry mate, I should look before I leap. I have lectrickary ign on mine. Dug out my old mag and it still throws a good spark after living in a box for 13 years. Ouch it bites.
Cheers
Title: Re: Does points opening ramp lead or trail.....
Post by: t20racerman on 19.07. 2013 22:04
Thanks a lot.

Happy now  *smile*
Title: Re: Does points opening ramp lead or trail.....
Post by: minibsa on 20.07. 2013 05:58
For another two cents worth - the ones on the left are later model and can be reversed by turning over the moving point and spring assembly. That sounds double dutch but maybe you can fathom it out!!     Bob.
Title: Re: Does points opening ramp lead or trail.....
Post by: muskrat on 20.07. 2013 10:34
G'day Bob.
I learn something new here every day. How do you adjust the point gap?
Cheers
Title: Re: Does points opening ramp lead or trail.....
Post by: bsa-bill on 20.07. 2013 11:56
Quote
How do you adjust the point gap?

Ah Bob was quicker to the keyboard than I was, yes I have a set like that, as far as I know without looking at the bike it adjusts exactly the same ( slotted hole and screw ) just the plate is bi-directional also (like so many things these days  *smiley4*)

Title: Re: Does points opening ramp lead or trail.....
Post by: RichardL on 20.07. 2013 16:45
Well, looking for information on this, I went to see what magneto.co.uk had to offer. Maybe I'm late to learn of this, but this useful business has closed operations, as the founder has decided to retire. This had been such an organized site with so much to offer that I hadn't even thought about the possibility that it was a small operation. I, for one, will miss the convenience of seeing all the mag parts with pictures all in one place and with online shopping.

Richard L.
Title: Re: Does points opening ramp lead or trail.....
Post by: groily on 20.07. 2013 22:46
The ones on the left are the later so-called 'low-inertia' steel contact set, set up for a magneto that turns anti-clockwise from the driven end - so the contact breaker turns clockwise looking from the clutch side of the bike. The ones on the right are a brass backplate set, as used until the steel assembly came along. The brass sets are handed - that set is for a mag that turns clockwise from the driven end. Which would suit eg Vincent, some Enfield twins, and some Douglas, as well as a large number of 4 cylinder Lucas mags on cars.
The adjustment of the steel set is car-like, and involves slackening the centre screw (which is slightly different from the one used with the brass part) and the other little screw that holds the steel bit to the backplate; the brass type involve just the lock-nut and screwed post on the fixed point. A steel assembly will go on any ringcam Lucas mag, but with brass, it has to be the right rotation.
One other difference between the 2 types is that with the steel assembly the 'live' point is the moving one, while on the brass set the live point is the fixed one and the sprung one is earthed. This matters if the spring blade should brush against the ringcam on the way round - the steel set will be shorted out (so no sparks), the brass sort won't - but might wear its outer spring blade away until it breaks!
Cheers, Bill
Title: Re: Does points opening ramp lead or trail.....
Post by: bsa-bill on 21.07. 2013 12:49
Quote
the sprung one is earthed. This matters if the spring blade should brush against the ringcam on the way round

or a wayward blob of grease bridges the gap (DAMHIK)

Thanks for that Groily - a little more info stored away
Title: Re: Does points opening ramp lead or trail.....
Post by: Greybeard on 21.07. 2013 13:13
I'd like to nominate all that information about mag points for the proposed 'Useful Tips', ( or whatever it was going to be called) section of this forum.