Lets talk magnetos.

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Seems to me, an adapter plate to mount a JH magneto on the timing cover, could incorporate a cable type advance similar to that used on the early Dommies. The entire magneto would rotate on the adapter plate to retard the timing for starting purpose. The OP states he has lathe and mills available to do a one off.

Slick
 
comnoz said:
They don't need one on the track because you never use the motor below 3500 rpm.

But they are much nicer on the street with an advancer. I have used the Lucas advance mechanism on the JH mag very successfully. Of course that was with the rear mounted mag which didn't last.

I ended up going back to the old Lucas mag which still works fine. Jim
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I think your post is answering some of the questions I had which I posted just after your post appeared. Want to know couldn't you fix the Lucas advance on a Joe Hunt magneto when it's side mounted? And if so, I'd really like to know the ins and outs of how you did that. I had an old Lucas magneto Matchless/Norton in the '60's and it was tickle the carbs and a kick to start. But I was younger then. Maybe I just kicked harder. (What's in the mind isn't in the mirror). And, surprise, no battery problems.
 
Generally if the timing is at full advance at idle, the idle tends to be touchy and the low speed performance is harsh. Pinging is not a problem as long as you do not lead the throttle too much.
The advantage to some programmable ignitions is the fact that you can reduce the advance a bit at higher rpm. At higher rpm the cylinder turbulence is high so the mixture burns faster. That means you can get a small power increase by reducing the spark advance a few degrees over 6000 rpm. [Not all progammable ignitions have this capability.]

And yes, I have done dyno test with a mag and a programmable crank triggered electronic. For best power throughout the rpm range the programmable wins. Jim

"Want to know couldn't you fix the Lucas advance on a Joe Hunt magneto when it's side mounted?"

No place to put it..
 
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comnoz said:
Generally if the timing is at full advance at idle, the idle tends to be touchy and the low speed performance is harsh. Pinging is not a problem as long as you do not lead the throttle too much.
The advantage to some programmable ignitions is the fact that you can reduce the advance a bit at higher rpm. At higher rpm the cylinder turbulence is high so the mixture burns faster. That means you can get a small power increase by reducing the spark advance a few degrees over 6000 rpm. [Not all progammable ignitions have this capability.]

And yes, I have done dyno test with a mag and a programmable crank triggered electronic. For best power throughout the rpm range the programmable wins. Jim

"Want to know couldn't you fix the Lucas advance on a Joe Hunt magneto when it's side mounted?"

No place to put it..
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Your answers were interesting. I've heard a lot if opinion, but was looking for something concrete. It would seem to say that backing off the advance for low rpm might serve very high rpm as well, but then the midrange would suffer. Still fascinated by the idea of ever increasing spark intensity with rpm -- and no battery, but now I have a clearer picture. I guess I'll have to save my money and wait for the heat resistant magneto with that perfect advance mechanism. Shouldn't cost Too much.
 
The idea of more spark available as the rpm raises sounds good but-
The maximum spark is needed when the cylinder pressure is the highest.

The cylinder pressure is the highest at low speed, heavy throttle, It goes down as the rpm raises and the cylinder does not have time for a full fill.

Unless you have a VE over 100% at some point up high which is a rarity on a Norton unless you have a supercharger.
 
I still don't understand why a magneto ignitions aren't developed with an advance mechanism for street vehicles. I already said that I understand that race applications probably don't need an advance since they aren't doing a lot of stop and go like vehicles in traffic.

None of the reading I've done about magnetos suggests that their design precludes an advance mechanism. I've read people's explanations for the lack of an advance that ranged from "it would cost more to make" to "It's made to be a simple as possible". I still don't see why a manufacturer in the modern technological era, wouldn't modify their magneto to have an advance function to make their magneto ignition an even more appealing choice for street vehicles.

... it seems to me, that there has to be some mechanical reason inherent to magneto design why they don't do it...

*******When My Dad learned to drive as a kid, he learned on a car that had an advance lever on the steering wheel, so as the engine went faster you advanced the spark. You also retarded the spark to start the car... This advancing of the spark timing was all replaced by the invention of distributors that automatically advanced and retarded through centrifugal force and also vacuum.

It just doesn't make any sense to me that the most popular magnetos made today have no advance mechanism, and more to the point, that there's no mechanical reason which precludes them from developing an advance feature to improve it's street-ability, yet these manufacturers don't persue what seems like an easy avenue of improvement...

Come on, seriously,... Why don't they commonly have an advance... ???
 
I've used and sold the Hunt mag for years. Mine is behind the cylinders and it uses the Atlas advance. The only problem I have had on my own mag is a failed condenser (once). The wire inside the condenser came loose. Easy fix with a new condenser. Try fixing a failed EI -forget it. I don't have them on my website anymore because they take time setting up the way I prefer, but I they are available special order. They are the easiest starting ignition I've tried - the bike usually starts when the kickstart is 1/2 way down. But nothing is perfect. I test each one before sending it out and once in a while there is a problem and I have to call the supplier. The coil failure that GGrider mentioned is probably because for a short time the magnets were too powerful and could burn out the coil. There should be one big and one small magnet on the armature. If they are both the same big size then it is a rare JH mag and one of the magnets needs to be down sized. Forget using a Lucas mag - there is no comparison to a JH. Morris also makes mags but not for a Commando. Morris does have a lever setup you can install to retard the timing on a fixed timing Commando timing cover type mag that hangs out in the breeze. Some think they look cool, some don't. I have a fiberglass silicone gasket on the behind the cylinder type that prevents oil leaks and I modify the armature so they are easier to time. Its really too bad that the rear mounts were dispensed with on the later Commando. They can be retrofitted but it requires machining.
 
Frankie17 said:
joe hunt magnetos quote $865 for a Norton Mag £657 GBP BTH K2F replacement £625 with shipping to the US only a few pounds more ?
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Remember I'm in Australia and the exchange rate in in the toilet. At the price Jim was selling them for, thats around $A1000 , the Britt one is $100 more.
jug
 
jseng1 said:
I've used and sold the Hunt mag for years. Mine is behind the cylinders and it uses the Atlas advance. The only problem I have had on my own mag is a failed condenser (once). The wire inside the condenser came loose. Easy fix with a new condenser. Try fixing a failed EI -forget it. I don't have them on my website anymore because they take time setting up the way I prefer, but I they are available special order. They are the easiest starting ignition I've tried - the bike usually starts when the kickstart is 1/2 way down. But nothing is perfect. I test each one before sending it out and once in a while there is a problem and I have to call the supplier. The coil failure that GGrider mentioned is probably because for a short time the magnets were too powerful and could burn out the coil. There should be one big and one small magnet on the armature. If they are both the same big size then it is a rare JH mag and one of the magnets needs to be down sized. Forget using a Lucas mag - there is no comparison to a JH. Morris also makes mags but not for a Commando. Morris does have a lever setup you can install to retard the timing on a fixed timing Commando timing cover type mag that hangs out in the breeze. Some think they look cool, some don't. I have a fiberglass silicone gasket on the behind the cylinder type that prevents oil leaks and I modify the armature so they are easier to time. Its really too bad that the rear mounts were dispensed with on the later Commando. They can be retrofitted but it requires machining.
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Jim, just putting my engine together now. Once its together (after having the cam bushes line reamed) and back in the frame ( stripping pc off to repaint and modifying in a few places ) will place an order with you.
I like the mag, EI's have left me stranded and I don't mind the look of the mag hanging off the timing cover. Rather cool if you ask me. When I ran a JH behind the cylinder on the 69, it ran faultlessly, always started first kick and needed virtually no maintenance. I like that. I don't understand the concerns about the need for an advance, never was an issue on the 69.
JUG
 
o0norton0o said:
I still don't understand why a magneto ignitions aren't developed with an advance mechanism for street vehicles. I already said that I understand that race applications probably don't need an advance since they aren't doing a lot of stop and go like vehicles in traffic.

None of the reading I've done about magnetos suggests that their design precludes an advance mechanism. I've read people's explanations for the lack of an advance that ranged from "it would cost more to make" to "It's made to be a simple as possible". I still don't see why a manufacturer in the modern technological era, wouldn't modify their magneto to have an advance function to make their magneto ignition an even more appealing choice for street vehicles.

... it seems to me, that there has to be some mechanical reason inherent to magneto design why they don't do it...

*******When My Dad learned to drive as a kid, he learned on a car that had an advance lever on the steering wheel, so as the engine went faster you advanced the spark. You also retarded the spark to start the car... This advancing of the spark timing was all replaced by the invention of distributors that automatically advanced and retarded through centrifugal force and also vacuum.

It just doesn't make any sense to me that the most popular magnetos made today have no advance mechanism, and more to the point, that there's no mechanical reason which precludes them from developing an advance feature to improve it's street-ability, yet these manufacturers don't persue what seems like an easy avenue of improvement...

Come on, seriously,... Why don't they commonly have an advance... ???
Click to expand...

No doubt -their main focus is racing.
 
"Try fixing a failed EI -forget it."

Oh, I don't know. It took my brother less than 10 minutes to put a new electronics plate in his tri-spark in a liquor store parking lot in Texas this summer.

Yes, I had one in my luggage, I've experienced "shake and bake" electronics before. In fairness, It was one of the earlier units.

And yes, it is hard to beat a hot mag for starting. Jim
 
But you have to admit that fixing an EI is super rare. When my Mag condenser failed I took it apart and was surprised to find a what appeared to be a roll of tinfoil in there. There's really nothing to it.
 
All I can say is my Norton idles perfect as soon as it starts, I ride around town and it sit very comfortable in top gear at 40mph and as soon as I open the throttle it never hesitates at all and will go to where ever you take it to, like Jim said it will fire up on 1/2 swing on the kicker so as soon as you kick it it fires not many EIs will do that.
Because the one I have runs directly off the end of the cam and if it had a advance unit on it as well it would hang out even more and if they want to put one inside the maggie there be no room for it , so answering your question I can't about auto advance all I know the maggie work perfect on my hot Norton without any problems at all, it starts easy, idles great, runs perfect all the time, no need to retard it when it starts easy the way it is.
After owning my Norton since new for over 42 years now I have gone with points and coverted to a Lucas EI which only lasted a year, then a Boyar after that but the first one lasted just over a year and the black box shit its self a 100 miles from home then the replacement Boyar lasted 32 years without any problem, the reason I wanted a JH maggie because the mount of batteries problems plus the weight of a heavy battery and I was running a JH on my Triumph which worked perfect.
People can make up their own mind about maggies vs EIs it don't worry me to me converting to the JH was the best thing I ever done to my Norton and over the years I have put up with that looks ugly out there, its got no auto advance, to me who cares what others think I love it, it works so well and I don't have any problems with telling people about it who want to know all I know it works for me and my friends who also have run JH maggies on their Triumphs think the same.

Ashley
 
Maybe off-topic, but related:

ARD used to make a microelectronic magneto, in my opinion the best of both worlds. I never researched what exactly goes on inside the tiny "black box" as far as advance curve, but it is (was) arguably THE best cam-triggered ignition system available for a Commando.

I am in the process of selling my '72 Combat Cafe Racer that has the ARD mag.

Lets talk magnetos.


Behind the little center cover is a pinhole; you set the crank to the static time position, assemble the guts of the magneto section with a special pin placed in the pinhole, tighten the rotor and stator in place, pull the pin, and you're done forever. The little black box is about 1/3 the size of a Boyer box. I have this one triggering a dual-lead coil.

One-kick starts every time.
 
Someone should produce the ARD again (with a couple upgrades).

Here's the info for GGrider - this could be the solution to his coil failures:

JH MAGNETO - 4 full size magnets are too much & can burn points (2011 earlier model, year is stamped into body), two full size & two ½ size is right, If both magnets look the same it is the too powerful 4 magnet style, If its the correct weaker style then one magnet is smaller than the other. Magnets are inside the armature under the steel. Use high capacity .34 microfarad condenser (made by standard and stamped S6-136) some condensers could be .12 microfarad.
 
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.
 
The optimum advance curve depends on a couple of things. The stroke and rod length determine the rock-over time which changes as the revs rise. Also at medium revs and large throttle openings, you can lose vacuum, so in the Dynatek system which is fitted to Harleys, a vacuum switch is used to cause the timing to drop onto a less aggressive curve if loss of vacuum occurs - which might cause detonation. In the end, three things need to be balanced - comp. ratio, ignition advance and mixture. When you use a magneto, you usually have fixed ignition advance with provision for retard when starting the motor. So there is another variable besides comp. ratio, which is fixed and that is not necessarily a bad thing. Theoretically there might be opportunity for performance gain by using variable advance curves and changing carb needle tapers. However in a lot of cases the simple answer is better.
I would much rather use a magneto than a Boyer. Batteries are a pain on a racer.
 
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 ?
 
comnoz said:
Out in the air there is no problem. Short rides behind the motor they will last quite a while.

One good long road ride with it behind the motor will do it in. Like a couple day trip across the country... Jim
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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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