Hello all
I have finally got round to renovating the magneto and a few things don't look to great. I have a few questions to put out there.
First of all, I note the armature assembly runs on bearings which appear to have insulating flower shaped gaskets between outer races and the casing. I don't have a mega but even a DVM shows quite low resistance between outer race and magneto casing. What should resistance be and can poor isolation here affect the quality of the spark?
Second, the bearings are quite worn and pitted; not surprising seeing likely to be 70 years old and might as well change them. Outer races and cages came out fine. The inners are tighter than a gnats chuff. Any advice /recommendations on pulling these off the armature with rudimentary tools. I see you can get some specialized pullers but don't want to get them for hopefully 1 off job.
Finally, on my suspiciouns of poor spark; although quite subjective it seems a good plan to suspect the condenser. I don't plan to pull apart the 'bobbin' and change condenser. I am planning to fit one of those 'brightspark' condensers under the points. Has anyone done this and can share experiences?
Cheers Neil
email (option): nlhclarke@gmail.com
There is no good way to remove the bearings without a special puller as you need to grab the outside of the inner bearing races. You can't get behind the bearings to remove them or you will destroy the slip ring. With the proper puller the bearings can be removed in a couple minutes. When you put the new bearings on, you will need to set the bearing preload with shims which means you may need to remove one bearing a few times.
As for the bearing insulating cups, there should be no electrical connection between the outer bearing race and the magdyno body. The cups are to prevent the spark from returning back through the bearings. The spark is supposed to return back through the grounding brush. If the bearing has an electrical connection to the magdyno body as you measured on your magdyno, the magneto will still work fine but is hard on the bearing as it will now have a spark going through it.
As for the bright spark condenser, I am not opening that can of worms. I personally would never use one and others can comment on their experiences.
'Brightspark' condensors can solve the problem if the condensor is the only problem...Bear in mind though that there can be other causes for a lack of spark...Fitting a Brightspark does nothing to address the potential problems of worn bearings, oil pentration, deterioration of the armature windings and insulating washers, pick up brush and earth brush condition, slip ring condition, strength of the magnets etc...
There is a good reason for the price difference between a 'Brightspark' condensor and a complete magneto overhaul...Ian
email (option): ian@wright52.plus.com
In about 2011 I took the plunge after speaking at length with Ken who originally had created the Brightspark device
At same time - I had an armature rewound without an integrated condenser & used the externally fitted Brightspark
It was a huge improvement over my old mag - that was quite tired - and since then has covered big miles with my m20 being my only old bike for many years
So - from personal experience- it works & works very well
Be it with my good armature
Whatever route you go down - a rebuilt armature is best route - with a condenser or with an externally fitted Brightspark - that will be your choice
If you have the mag apart - new bearings - cheap - with new insulators are highly recommended- watch that the bearings haven’t spun in the housing & are not arcing to ground
Brightspark website provides oversize insulators for this reason
Jo’b
email (option): Jonnyob1atgooglemail.com
At same time - I had an armature rewound without an integrated condenser & used the externally fitted Brightspark
It was a huge improvement over my old mag - that was quite tired - and since then has covered big miles with my m20 being my only old bike for many years
So - from personal experience- it works & works very well
Be it with my good armature
Whatever route you go down - a rebuilt armature is best route - with a condenser or with an externally fitted Brightspark - that will be your choice
If you have the mag apart - new bearings - cheap - with new insulators are highly recommended- watch that the bearings haven’t spun in the housing & are not arcing to ground
Brightspark website provides oversize insulators for this reason
Jo’b
I bought the bright spark ages ago so will use it. However, I'm going to try a minor bodge and not remove the old one. IE don't do the full 'condensosectomy' procedure as the bright spark blurb calls it. My logic depends on the old one being open circuit so putting new one in parallel should be ok ? I guess if it failed short circuit I'll still be where I am now and will be forced to dismantle the armature. Can anyone say if removing the old one is easy or not?
Are there any winding resistances/ isolations to check?
Cheers Neil
email (option): nlhclarke@gmail.com
I do not want to start a long discussion about Bright Spark condensers but carry a spare if you are using one.
The following quote is from Bright Spark Magnetos:
".....to provide a magneto condenser that could be treated as a simple, regular service item by the home mechanic. Whether the thing lasts for five years or fifty-five years is not a concern for the market we're aiming at."
So they are admitting it is an item with a limited service life and will require replacement one day. If I am going to the trouble to replace a magneto condenser, I want one that will last forever. Modern condensers are much better than anything Lucas ever used and better than what Bright Spark is offering. As Bright Spark is mounting it to the points plate, they have to use what will fit in the available space instead of what is the best condenser for the job.
If you can take the armature apart, the condenser is easy to replace with a proper one.