I like what Magnetoman writes, it makes sense to me, my only problem is, out of all the magneto re builders out there who do I send my magneto to whom will do the job as well as Magnetoman describes?
Poor starting on new Amal and BTH Magneto
- Thread starter minivin
- Start date
Oh well, no response, back to the drawing board.
Hi Peter, contact me by email and I can send you the details of a local chap, near Hailsham, who can do exactly what is needed but the turn round time is likely to be about three months.
Hello Peter, There was another thread, On the same theme, And " A-HRD" Down Bristol way Thought a lot of his Man, Send him a PM, Cheers Bill.
Indeed, I did rate Sean Hawker extremely highly. But he took so long to rebuild a mag properly that he had a massive waiting-list and in the end he got all stressed about it and couldn't make enough money doing it. He's recently packed-up, closed his website and got a "proper" job doing full-time electrical work for Network Rail. Shame. Fortunately, all my bikes are running his restored mags, dynamos and regulators - so I'm not expecting electrical problems anytime soon. (Eek, that must be tempting fate - but we'll see).
Peter B
Bristol, UK
This is certainly part of the problem. Even if I took on magneto repairs for others part time, if I charged what I would have to in order to compensate for work I wouldn't be doing during that time, a straightforward rebuild would cost over $1000 for the labor alone (and, if you're thinking of asking, no, I'm not interested in doing it even at that price, because I have too many other things I'd like to do with my time).
If you haven't seen it, I discuss the costs of rebuilding magnetos, and offer advice on what to look for in a magneto rebuilder, at:
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=464907#Post464907
Just buy one of the exchange armatures off ebay and rebuild it yourself, provided all your parts are in good condition. I've rebuilt dozens of them and they're not that hard. Provided the armature is fitted with a good condenser and windings of the correct guage..all should be ok...in old magnetos it's the windings that break down over time causing hard starting when hot....every one always blames the condenser....i''ve found this is not the case. There is too much fear factor with magnetos.....Just give it a go. I agree that there is no money to be made rebuilding them, thats why its hard to find people who do it correctly, and generally retired auto electricians are the ones.....but i dont think there was such a thing as an apprentice magneto rebuilder anywhere....indeed with any restoration work, there is no money in it....a labour of love....too time consuming....you have to be a true enthusiast to do it......like many of you.i have been doing it for a long enough time, so i think i have some idea.....At least i still enjoy what i do though........Greg.
I have to disagree with you. With post-WWII magnetos, it's almost always the condenser, and less frequently also the windings. Again, if you haven't seen it, you can read the results of a very detailed study I did of post-War Lucas condensers (and why it is inevitable they will fail) at:
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=466579#Post466579
Back to your initial assumption, "provided the armature is fitted with a good condenser...". Therein lies the rub. Any number of incorrect replacement condensers have been, and are, recommended and offered for sale over the years. The problem is that a magneto condenser is subjected to a very high current pulse when the magnetic field collapses, and that isn't a specification of much importance for the capacitors required for a lot of items manufactured these days. Hence, most types of capacitors picked from a catalog will have internal connections too thin to survive those pulses for very long (some still manage to survive surprisingly long despite this, but fail they will). Judging from the number of professionally restored magnetos that have failed because the replacement condenser went bad, I have to wonder about what is in the rewound armatures sold on eBay.
Slip rings are also a big problem area. Looking back over the 135 magnetos with 'electrical' problems that passed through our workshops in the last 12 months:-
Condensers
http://brightsparkmagnetos.com
Condensers
- Every magneto that still had an original paper condenser (mainly Lucas) needed it replacing.
- Most magnetos that still had an original mica condenser (mainly BTH and early Lucas) didn't need it replacing. Nevertheless, about half of those customers still asked for the condenser to be replaced by a condenser mounted in the contact breaker assembly rather than in the armature, to facilitate future fault-finding.
- About 50% of magnetos had previously had their condensers replaced. Of those, over 90% of the condensers (or in a few cases the resin in which they had been potted) showed signs of breakdown, some serious so that the magneto was unserviceable, others just early days so that there was some degradation in performance, but a sign of things to come.
- 54% of the armatures were given a rewind. Of those, a few were rewound at the customer's request, even though they were still good. So, about 50% actually needed a rewind.
- Of the original windings that came into the workshops, most needed a rewind.
- Of the armatures that had previously been rewound, most didn't need another rewind.
- Of the armatures that needed a rewind, most had lost a significant amount of their insulation (shellac), about 50% had a break in the HT winding, and the remainder just didn't perform well on our coil testers. Often bad performance only showed up when the armature was warm.
- 62% of the magnetos had their slip rings replaced. A small proportion were broken. With a few, the track was too deeply grooved to be skimmed. With a few, we couldn't get a good connection between the HT winding and the slip ring, due to previous arcing in the hole in which the spike of the HT winding fits. But the vast majority that needed a new slip ring exhibited electrical breakdown of the plastic, particularly when warm. It's not uncommon for a leaky slip ring to require 50% or more break current in the LT winding in order to achieve consistent sparks from the magneto.
- 19% of the magnetos needed a new pick-up, a few because the old pick-up was broken, but the majority because of breakdown of the insulating material, again particularly when warm. Only one had actually blown a hole through the plastic. It was interesting to watch the sparks on the test rig ... until the thing caught fire.
http://brightsparkmagnetos.com
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More on condensers . This is an old telltale method to see firsthand if the condenser is indeed at fault , needs replacing .
Remove the Bakelite end cover and start the motor , switch off the lights in your garage , must be in the dark . Observe the whirling point assembly . There usually a rare errant bit of spark seen at the points , tiny flashes , not constant . But if a steady flame is seen spinning quite regularly at every point break , THEN your condenser is not doing its job , badly needs being tossed out . This sparking is eating up the points all the while during operation . Preferably replaced with freshly produced , NOT a nos item . all old stock Lucas pieces are around 60 years old and are suspect .
Be aware that sparking contacts produce OZONE gas which is corrosive , thus the need for a small air bleed hole in the contact cover to let it escape . Sid .
Remove the Bakelite end cover and start the motor , switch off the lights in your garage , must be in the dark . Observe the whirling point assembly . There usually a rare errant bit of spark seen at the points , tiny flashes , not constant . But if a steady flame is seen spinning quite regularly at every point break , THEN your condenser is not doing its job , badly needs being tossed out . This sparking is eating up the points all the while during operation . Preferably replaced with freshly produced , NOT a nos item . all old stock Lucas pieces are around 60 years old and are suspect .
Be aware that sparking contacts produce OZONE gas which is corrosive , thus the need for a small air bleed hole in the contact cover to let it escape . Sid .