petert120r wrote:Why would you want to do this? A K2F rebuilt by any of the specialists for around £200 will give you independent and reliable sparks for more years than you're likely to need.
Or you can do a exchange with the club over the counter.
I'm exploring all the possibilities, I'm getting my K2F done by Dave Lindsley anyway. I did not see anything about 'exchange magnetos' on the spares pages? (Too late now...)
Each to their own of course.
Why have a 60 plus year old system when you can have up to date kit that works on your 57 year old bike. Not much we can do to improve engine design, but by all accounts a modern electronic ignition system with exact timing and electronic advance retard is regarded by those that have fitted them as being the best modification they have done.
GOOD spark at ALL revs. Not WEAK spark at kick speed. No power drain turning an armature. No capacitor (condenser) to break down. No awkward points to set every 5,000 miles. No re-timing (cover off) when points are re-set. No windings breaking down when hot.
A 50 year plus magneto needs to be re-wound and re-magnetised. New oil seal, bearings and slip ring. New points. New capacitor. New pick ups. Points opening cam ground to give exactly 180 degree equal spark AND equal points gap.
I very much doubt you'll get that in a £200 re-build! Ask your chosen repairer if he plans to do all that.
We've sent magnetos away at work, and VERY little has been replaced.
Fair comment, Trevor, but as you say, each to his own.
I prefer the mag as it keeps the bike original, has a certain magic/mystery about it, looks 'right' and doesn't depend upon a well charged battery. My 'short' Lucas 6v dynamo with a claimed output of about 42 watts (if in tip-top condition and at 40mph) struggles to run just the running lights. I could ride my mag ign bike day or night without lights but not without sparks
I have read that mags were discontinued by manufacturers mainly because a coil system was cheaper to produce.
Mag ignition vintage and modern aircraft engines seem to be fairly reliable.
'There is a tide in the affairs of men
Which taken at the flood............'
I have contacted Wassells to see if their electronic system would work INSIDE the timing cover. I wanted to make a mounting (from the magneto studs) to hold the stator and run the rotor from a thin (Plastic/nylon) gear running on a dummy shaft inside an otherwise empty magneto. Alas, they state, DO NOT use in oil or in oil mist. That would have resolved the 'keeping it looking original' problem.
No use comparing old motorcycles to aircraft. They MUST have reliable ignition. Development has also taken place to bring their magnetos up to date with modern materials and machining. Ours are over 50 years old. AND how much do they pay for a modern mag? Probably thousands. For bikes we are talking hundreds.
The kit I described should cost no more than £300.00 all in PLUS installation. However if you really want to stick with a magneto, how about one from BT-H? Their modern K2F replacement magnetos are available for £750.00.
All about cost.
Modern aircraft mags I'm not familiar with, but I think anyone who took a good look at a typical period 4 cylinder mag for a car side by side with the similar unit for a light aircraft, would be quite surprised at how few are the differences Trevor.
Screening, yes, to avoid interference; a bearing here and there where the terrestrial beast might use a bush (on eg distributor shafts). But pretty similar. Much of the (old) BTH range used in many pre-war cars was a direct descendant of their experience on aircraft for the military. The safety factor comes from having two of the things on machines that go upwards.
There's no real reason to suffer a bad magneto, and £300 plus installation would get a pretty decent one in most circs. They aren't second-rate devices, certainly not, but of course they aren't state of the art either. Not surprising when one remembers that the basic high tension mags made over 100 years ago are not much inferior to instrumenst made as late as the 1960s. Magnet steels improved, laminations helped electrical performance, contact breakers improved, etc etc - but the original units made by folk like Bosch (in particular) were tremendous things straight out of the box. British companies like BTH fully maintained the standard, and Lucas and others weren't far off, and doing it at ridiculously low cost for the major manufacturers.
So you're quite right, a mag won't come with a built in advance/retard function, it might need tweaking to get perfect firing intervals, it won't generate 30Kv sparks at nil rpm, it won't operate on the spare or dead spark principle. But it will be perfectly adequate to start and run pretty well any elderly motorcycle, even with high compression, and do it first kick as often as not.
Whether any of the present offerings in the 'modern' idiom will still be running and repairable in 50 years or more, none of us will probably live long enough to know. But I have some doubts!
Purely personally - and this really is a 'Marmite' subject of 'love 'em or hate 'em' - I like 'em same as Spriddler. Certainly I prefer them to the basic battery and coil systems of the sixties (especially the fiddly twin-points set-ups) and I haven't found the advantages that are often claimed for the likes of Boyer Bransden necessarily stack up in practice, with sensitivities at switches, requirement for constant battery voltage for correct operation, etc.
The modern BT-H unit is a very fine thing, and nicely made by good people. But they can go wrong too, as I've seen for myself 'ere now - and repair costs are not as low as one might think. Replacing the triggers and little coils can easily come to the sort of prices people have mentioned in this thread. And there is little chance of DIY maintenance at any level with them, or with most electronic systems.
For those reasons, I think a lot of folk prefer the old kit, while fully respecting the advances that have been made in the recent past.
I was an aircraft engine fitter for 22 years in the RAF, including Chipmonks and Shakletons, so know all about aircraft piston engine magnetos. They are 'duplicated' and often massive, as well as screened and very expensive. That on the RR Griffon was two mags in one casing; the Merlins I worked on (privately owned aircraft) had two separate mags. It was amazing just how much 'Mag-drop' you got on engine runs;...this is where you switch off one mag and run on the other alone. Their combustion chambers are so big the loss of one plug (two per pot) drops the max-rpm! My G12 armature is costing £150 all in, a new Wassell unit is over £300. When I went to the Post Office to send it to Dave Lindsley, the girl asked me what the parcel contained, I replied, " A magneto armature." She then asked if it had any batteries in it..........
