b31 ignition

[b31newbie]

Hi

I've just joined and am new to old bikes. I've had a 1950 b31 for a little while and it seems to have a problem with the points that I can't work out. It runs for a while (10 miles ish) then cuts out. Leave it to cool down and it's fine again.
I'm wondering whether it would be better to just change to electronic ignition and just sort the whole thing out for once and all.
It runs on 6 v electrics with + earth.

Can anyone advise on which ignition system to buy, because it seems a bit of a minefield to someone as inexperienced as me. And I don't want to pay someone to do it, I want to do it myself.
Thanks and hello  

[bikerisme]

might be the condenser try a new one you can run electronic ignition on + or - earth not sure about 6v? look on boyer bransdon web site you should be able to get an answer from that or you can phone there help line

[L.A.B.]

It runs for a while (10 miles ish) then cuts out. Leave it to cool down and it's fine again.

Hello,

A 1950 model BSA B31 would normally have a 'magdyno' (magneto and dynamo incorporated into a combined unit, rather than battery/coil ignition fitted from 1958) so could you confirm what is fitted please magdyno, or battery and coil ignition?

If it is fitted with a magdyno, then the condenser/capacitor or windings of the magneto could be breaking down due to old age, so may need overhauling by a specialist?

When it does cut out, presumably there is no spark at all, or is there only a very weak spark?

It runs on 6 v electrics with + earth.

Can anyone advise on which ignition system to buy, because it seems a bit of a minefield to someone as inexperienced as me.

I would need to know the answer to the magdyno question before attempting to advise you further.

[b31newbie]

Thanks for replying.
As far as I understand it, it has a magdyno fitted, nothing has, as far as I am aware, been changed from std.

Yes when it cuts out, there is no spark or a weak spark. When someone played with it for me, who knew more than I did, he managed to get it going by mucking about with the points. But there seemed to be nothing wrong with them in the first place tbh.

I'm more than happy to learn, but I can't go from standing to 100 mph in a week   much as I'd like to.

Btw, when I just was trying to start it, the petrol tap started leaking, it's actually coming from the slot that the push/pull lever goes through, does this mean it is a new one needed, or if I take it off, can it be fixed?

[L.A.B.]

I'm more than happy to learn, but I can't go from standing to 100 mph in a week   much as I'd like to.

If it's any consolation, I don't know much about them myself, as I've never had a bike with an ignition magneto!

So as I see it, you have three choices, find another one that works? Have the original one repaired? Or fit an electronic magneto conversion?

http://www.magneto.co.uk/

http://bt-h.biz/index.htm

Here's some good info on magnetos: http://www.bolsover.com/lucas/index.htm

    

Btw, when I just was trying to start it, the petrol tap started leaking, it's actually coming from the slot that the push/pull lever goes through, does this mean it is a new one needed, or if I take it off, can it be fixed?

They are normally rebuildable, so it probably needs a new (cork?) seal?

[Rex]

It's a common fault with old mags, so budget about £100-140 to sort it.
Sounds steep, but it'll never let you down again.....

[b31newbie]

OK thanks.
So, if it's a common fault, does it always show itself in this way?

Looking at the prices of electronic conversion kits, it seems alot more expensive to do that, rather than repair the original.

Would it be better to remove the magneto myself and send it off to be repaired, or would it be better to take the whole bike in somewhere?
And by better, I suppose I mean cheaper, or having a better job done.
Would anyone have any advice of where to send it, as I presume that will be the better choice?

L.A.B thanks for the info on the petrol tap, I got it sorted straight away. One thing you can say for these old brit bikes, is that they are built solidly and everything on them is able to be rebuilt without throwing anything away. A refreshing change!

[Rex]

OK thanks.
So, if it's a common fault, does it always show itself in this way? [/i]

Usually the capacitor and/or armature ages and acts just like this. Just send the armature off for rebuild (it's where the cap is too). Some like the electronic mag conversion, but I like to KISS, so a mag does it for me every time.

[b31newbie]

Can you advise how to get the armature out?

I do have a BSA service sheet book, but it doesn't seem easy to understand (for me, I'm sure) do I need any special tools?

[Rex]

Although I've never worked on a B31,Lucas mags are pretty generic. Once the mag is removed from the bike and the various brushes removed from thier 'oles, the points assembly removed and the end-cap taken off, then the armature should slide out.

Oh, and don't forget the safety screw if fitted...