Lets talk magnetos.

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oldmikew said:
perhaps i missed a trick back in the day, but my Super Rocket had Lucas magneto.. i was not aware that they had separate stock numbers for different applications ie one for triumph ,one for bsa one for norton etc.Lack of sparks meant a trip to the breakers to pick up a mag for a couple of quid. And it had manual advance retard . starting it on full advance would induce a vicious kick back . Have to say they seemed to be rubbish.. it was almost impossible to get the same timing on both cylinders... In contrast the lucas magdyno fitted to my ES2 has given 50 years service. now alas it needs reconditioning.
So I would say on single cylinder applications they are better than on twins.
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Re; “it was almost impossible to get the same timing on both cylinders”

This was easily solved by the magneto experts by getting the mag to fire 0 and 180 degrees – I had mine done .
 
Bernard,
With fixed timing ? I actually bought a Lucas exchange Mag £25 and fitted when the engine was taken up to RGS spec. A huge amount of money in todays terms 1and ahalf weeks average earnings.. It was 15 degrees out, Lucas sent me another cam ring that was little better. Judicious work with an oil stone gave some improvement .
 
I was guessing that the mechanical design of a magneto doesn't lend itself to the addition of a centrifical mechanical advance of some sort or it would be a common on them... No one need regurgitate their love for magnetos as a response to my question. I wasn't questioning your choice. I was only asking a technincal question about their form and wondering why they don't commonly incorporate an advance function into their design.

I see that some magnetos have a retard lever for cold starts, yet few have an advance mechanism... Spark timing control would be an improvement, so I wondered if something about the basic design of a magneto made designing an advance mechanism for a them problematic, or is it just that they are so much more used in a racing applications where the advance curve isn't needed because the engines run at high rpms continuously.

I aways wanted to have a magneto elegantly mounted on backside of my timing cover to give my bike a bulletproof ignition, so even if the "prince of darkness" struck my electric system dead on a ride, I could still ride the bike home in daylight. Electrical problems was the reason the bike was sold to me. It's previous owner was baffled and disgusted by the bike's problems. Even after I fixed the electrical issues, the paranoia of electrical failure fueled my curiousity with a magneto conversion. I supose after all these years of good performance after I straightened out the electrical system, I should let go of my paranoia, but that doesn't keep me from being curious about magnetos and their design...

sorry if I derailed this thread. I hoped to learn something with my questions. I wasn't challenging anyone's choice of ignition system.
 
"Then why not insert a small plastic funnel under the fork yolk and run a black hose pipe to the magneto at the rear of engine to keep it cool;)"


It might work.

I am rebuilding a motor for a customer that was running a JH mag behind the motor until it died from heat. He is planning on trying it again with a insulating gasket and a shield to keep the hot air off of it. We will see how it works out.
 
o0norton0o said:
I was guessing that the mechanical design of a magneto doesn't lend itself to the addition of a centrifical mechanical advance of some sort or it would be a common on them... No one need regurgitate their love for magnetos as a response to my question. I wasn't questioning your choice. I was only asking a technincal question about their form and wondering why they don't commonly incorporate an advance function into their design.
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Lucas and BT-H magnetos were commonly used with an auto advance.

I see that some magnetos have a retard lever for cold starts, yet few have an advance mechanism... Spark timing control would be an improvement, so I wondered if something about the basic design of a magneto made designing an advance mechanism for a them problematic, or is it just that they are so much more used in a racing applications where the advance curve isn't needed because the engines run at high rpms continuously.
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The "retard lever" on a magneto as fitted by Norton, retards the timing from fully advanced. Then, rather obviously, you can use it to advance the timing to the fully advanced position again.
 
oldmikew said:
Bernard,
With fixed timing ? I actually bought a Lucas exchange Mag £25 and fitted when the engine was taken up to RGS spec. A huge amount of money in todays terms 1and ahalf weeks average earnings.. It was 15 degrees out, Lucas sent me another cam ring that was little better. Judicious work with an oil stone gave some improvement .
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Timing discrepancies can be corrected by stoning the cam, as said above, or by lopsidedly shimming the points housing.
 
The difference in vacuum at various throttle openings is usually compensated for, by the shape of the needles in the carburettors. There is probably an optimum ignition advance for most fuels in particular engines, but in the end, the adjustment is usually made by changing carburation. An advance curve probably acts in much the same way as the taper on the needle to achieve optimum combustion conditions in the cylinder head. There are probably performance gains to be had by playing with advance curves and various taper needles. However most of us would never bother to go there. With a magneto, the comp.ratio and ignition advance are fixed and we simply jet to them, so there is much more likelihood of getting of getting the setup somewhere near right. If you were playing with advance curves and different taper needles, the number of variables is increased and it is that much more work.
 
acotrel said:
Just looking at a Commando motor, you would think that the magneto arrangement from an Atlas might work with a bit of machining - apparently not so ?
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They can be made to fit, but it does require some machining of the case and timing cover, and the use of Atlas timing side parts, as well as either an Atlas cam or custom spacer and bolt to allow use of the Commando cam. I think we've already covered that conversion in more detail somewhere here on the forum. Ron Wood used Lucas racing mags in the Atlas location on his Commando based race engines, as have several others. I ran a 920 with that conversion, but with an early ARD mag in place of the Lucas. It worked pretty good, but had a tendency to fry the mag coil. Maybe from heat like comnoz mentioned. I used it until I broke the cases, and then switched to electronic ignition, and later to an ARD mag in the Commando points location. I'm still using that one.

Ken
 
I may be a little confused here(often more than just a little!) But I thought BT-H magnetos had a mag for the Norton Commando that used a solid state device to create an advance curve and trigger the spark. Something about "the best of both worlds". Is this really a mag and if so, is it a good one? Also, it mounts behind the cylinders I think. So, are they using the rare earth magnets and, if so, have they solved the heat problem? But I might have been mistaking a Lucas rebuild with a new design.
 
BT-H does indeed make a magneto that will replace the original Lucas mag, and it does mount behind the cylinders, just like the original, but not on a Commando, unless you do the machine work to convert it to an Atlas style timing side configuration. They make electronic models with a built in advance curve, as well as models without an advance curve. But if you convert your Commando to the Atlas style, you get to use the Atlas centrifugal advance mechanism, so you don't need any advance in the mag itself. That means you can fit a Lucas, Joe Hunt, BTH (without advance), old ARD, Fairbanks Morse, etc.

Ken
 
lcrken said:
BT-H does indeed make a magneto that will replace the original Lucas mag, and it does mount behind the cylinders, just like the original, but not on a Commando, unless you do the machine work to convert it to an Atlas style timing side configuration. They make electronic models with a built in advance curve, as well as models without an advance curve. But if you convert your Commando to the Atlas style, you get to use the Atlas centrifugal advance mechanism, so you don't need any advance in the mag itself. That means you can fit a Lucas, Joe Hunt, BTH (without advance), old ARD, Fairbanks Morse, etc.

Ken
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I just got a reply back from BTH. Very nice. He will send more info about the advance curve. I'd like to hear from anyone who has used one.
 
Aesthetically this....

Lets talk magnetos.
Is either Steam Punk, or........

Lets talk magnetos.
Bosozoku
 
comnoz said:
I am rebuilding a motor for a customer that was running a JH mag behind the motor until it died from heat....
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This doesn't make sense to me. I ride in Fresno summer temps of 110+ deg with a mag behind the cylinders and it idles perfectly even when overheating at stoplights. If anyone would overheat a mag it would be me s but I've never had a heat problem with a modern JH. Never had a magnet lose power and don't know of anyone else who has had a heat problem with a modern JH including racers (other than the occasional defective coil). Maybe GGrider knows otherwise but he could have the wrong magnets in his armature (early 2011 defect). Is this an older JH mag before neodymium magnets? Check the stamped date on that JH mag to see if its an early 2011 with the wrong magnets.
 
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jseng1 said:
This doesn't make sense to me. I ride in Fresno summer temps of 110+ deg with a mag behind the cylinders and it idles perfectly even when overheating at stoplights. If anyone would overheat a mag it would be me s but I've never had a heat problem with a modern JH. Never had a magnet lose power and don't know of anyone else who has had a heat problem with a modern JH including racers (other than the occasional defective coil). Maybe GGrider knows otherwise but he could have the wrong magnets in his armature (early 2011 defect). Is this an older JH mag before neodymium magnets? Check the stamped date on that JH mag to see if its an early 2011 with the wrong magnets.
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I'm sure you know I'm interested in magnetos. That said I've heard "first hand" accounts of mags dying because of heat And about mags -- the same kind -- NOT dying because of heat. I got in touch with BT-H and was told that their mags now use heat resistant magnets. So there must be, or have been, something to the heat problem, but perhaps it's now solved. I'm 100% sure all the mag manufacturers have investigated this thoroughly. It seems important enough that they should be consulted (avoiding an advertising effort) and this should be reported on in a factual way. I'm in engineering and, just from work experience, I am sure there are a thousand papers, each having been subject to peer review, on this very topic. And there are members here with first hand experience who know exact types and dates of manufacture more than "the mag failed because of heat" (or didn't). Not being critical of anyone, when you add to a blog you don't (and probably shouldn't) put in every last detail. Perhaps this has already been addressed here on this site. If that's the case apologies all around.
 
Bernhard said:
Then why not insert a small plastic funnel under the fork yolk and run a black hose pipe to the magneto at the rear of engine to keep it cool;)
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A small vane or air scoop, judiciously mounted on two of the rear timing cover screws, would be much more effective.

Slick
 
Perhaps heat kills the condenser or stuffs the internal wiring and the magnets get the blame ? I once dropped my bike on the road and the magneto died. I used a rotating magnet magneto on a race bike for 12 years and never had a problem, even though the motor was enclosed within a fairing. Of course that is not the situation you get with a touring bike in desert conditions.
 
 
Just as a point of reference, my 37 year old Boyer lights the fire first kick, warm or cold, (unless I've failed to provide fuel in a palletable mix), and for 38,000 miles, no hiccup. :D
 
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Triton Thrasher said:
Any bike that doesn't do that has a fault.
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I was chiming in in reference to some of the romantic verbiage like this:
"I now have a newer Joe Hunt maggie on my hot Norton it has the 4 rare earth magnets and man does it kick arse, it has been on my Norton for over 7 years now with no problems at all and is also a first kick everytime, the first kick for the day you have to give it a big kick but after its been started for the day it will fire up on half a swing on the kicker and I can do that sitting on the seat.
They cost a bit to buy but once set up it will last a life time of trouble free use"
 
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