Lucas MO1 magneto

[nige63]

I have got it on the bench and with a drill attached and the ht lead with no plug or cap i am getting a very thin spark. Any ideas.

[Steve.S]

The spark should jump a 5/16" gap. Assuming the points are clean and set to 0.012", I would have a look at the Brightspark website for inspiration.
In my experience, the armature will require a rewind and new condenser, but you may be lucky. I would recommend APL for rewind if required.

[Greenfield]

Start with the simplest, is the HT lead any good? Is it making a good contact where it enters the mag?
Are the points clean and gapped correctly? Is the points area clean so that there is no short to earth?
If everythings good so far, we're probably looking at a magneto overhaul. Try Priory Magnetos.

[nige63]

Thanks for the info. All new points and a easy cap condenser. Will give priory a call.

[Rog1]

I had such a thin spark from my MO1 magneto that I couldn't start the bike. I stripped the magneto down (not difficult since you've already got it off the bike) and measured the windings. The LT winding was spot on at about thirty Ohms, but the HT winding was nearly two million Ohms instead of three to seven thousand.

I went for a Thorspark conversion. This bypasses the magneto and uses a pickup in place of the face cam, and a widget with a magneto that spins round, where once the points did. It all comes in a kit with an ignition coil but it only uses a quarter of an amp, say Thorspark. It's £150, half or less of the cost of a magneto overhaul, plus it doesn't take too long to fit, instead of waiting for the magneto to be returned after overhaul.

But strip the magneto apart and you can check everything. There are cardboard insulators around each magneto bearing and they may be in poor condition, or there's oil over everything because the oil seal in the timing chest has failed or maybe there's an engine oil leak. As Steve S. says, the Brightspark website is very helpful, and they have detailed inspection instructions which I found very useful:http://brightsparkmagnetos.com/DIY/index.htm


Good luck.

[nige63]

Thanks Rog1 that's some great tips will test today.

[Rog1]

and a widget with a magneto that spins round, where once the points did.

Whoops! I meant, "and a widget with a magnet that spins round, where once the points did."

[neil1964]

The MO is a very simple piece of kit and in god condition you should get a decent spark using a copper core HT lead to the mag body just by flicking with your wrist.
I had my first mag checked over and rebuilt by Brightspark (it went on its 'Jollies' to France for a couple of weeks and came back in A1 condition using my existing armature, new cap, slip ring and bearings.  Bill was very helpful.
Since then I've read more and stripped and repaired a couple myself.  I have AVO MkVIII, Megger and Fluke.  I also have the bearing removal tool (a simple DVM and the bearing tool are the essentials).
I had my armatures rewound by a gentleman in Bristol.
So far so good but I think that there are a few poor quality slip rings and points knocking around.
I use copper wire (with soldered brass ring on the HT pick up side), non suppressed cap and non-resistor plug set at 18thou, points at 12thou.
The above posters have pointed you to good sources but once you are familiar with them mags are pretty good. 
Having said that if I were totally confident with the battery charging system and one of my mags failed I would certainly consider going down the Thorspark route

[nige63]

Thanks neil1964

[nige63]

Hi any tips on removing the inner race bearing

[neil1964]

You have options:
Buy an extractor (two types)
Make an extractor tool
Strip it down and get someone else to do that but for you.
Cut the old one off
I bought an extractor from flea bay a few years ago.

[nige63]

Thanks neil1964. Once cleaned up they look ok so going to leave them.

[neil1964]

Thanks neil1964. Once cleaned up they look ok so going to leave them.

That is good
Can you still split the armature?  You will need to remove the capacitor which is paper type and the failure of which is the cause of the majority of the woes of a weak magneto (particularly when hot).
You can do a 'condensectomy' through the access holes but you need to know what you are aiming for and be able to reattach the wires, then you can use one of 'http://www.brightsparkmagnetos.com/'surface mount caps.

[nige63]

Do I need to do that before I fit the thorspark

[Rog1]

No, you don't; the Thorspark is electrically independent of the magneto. All my magneto does now is spin the widget with the magnet around, in time with the engine. The kit comes with the widget, the pickup, cable, a mini blade fuse (2A) and holder and various fixings, the coil, a coil bracket, an HT lead, and detailed instructions. But I set the magneto up as though it was working, with new insulators and the proper end float etc because it was the easiest way to do it.

You'll need to fit a switch to stop the battery running down and so that you can turn off the engine. Thorspark sell a simple key switch, but I bought an ordinary classic bike type off/on switch which fits on the handlebars and means I didn't have to make a bracket. This switch is on the battery side of the ammeter, and disconnects the battery, the new ignition circuit and the lights; I can't forget to turn the lights off then come back to a flat battery.

I did need a little more cable than Thorspark supply, but you might be alright, depending on where you fit things.