Joe Hunt mag. Pro’s and Con’s for a tuned motor...

When you talk about Joe Hunts you should consider how old they are. The new model with the neodymium magnets is an improvement over the older type. What I like about is mag is that you can repair it - replace the condenser & points or coil. With an EI its usually toast when it fries.

oldmikew said:

Nigel ,I wonder if Steve or Minnovation have any of his EI kits. As you are not fitting an alternator surely this would be the way to go for you are not getting the variations induced by the camshaft. Would it be difficult to modify a basic pazon or boyer to run off the crank ? Or perhaps one of them would advise on a suitable single cylinder unit

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Steve’s system is an option, albeit still a total loss type system.

Rex Caunt Racing built my ignition system for the race bike, crank mounted, batteryless.
He doesnt show them on his BSA website , although Im sure he will still build you one if you pester him.

Non programmable though

Sorry , no JH experience for me other than watching one carousel off a Commando during a track day.
He over filled his oil tank, went down in front of me and took out my mate on his Triumph, thought he had fixed it after the off, took it out again to have it fly off, hence the carousel effect complete with plug leads !!!
They are hardy though , he had it together by the end of the day.
Regards Mike

If it was easy to fit a magneto to a commando, I'd be using my Lucas competition magneto and not my Boyer and battery. I don't doubt it is possible to get more performance by using a programmable ignition system and playing with the tapers of the carb needles, but the benefits might be marginal unless I decided to use petrol as the fuel. One thing which was mentioned in the article on the RD400 in Motorcycle Classics - with the closer gear ratios, the tach needle doesn't drop so far as you work up through the gears, so the motor tends to bog down less. With a Commando, the higher you can keep it spinning as you change up through the box, the faster it accelerates. If you were using wider ratios, you depend on the motor spinning up on the throttle, so improving throttle response is more important than when you are using close ratios. The methanol fueI I use allows me to have much more tuning leeway.

As Jim has just said the old JHs were two rare earth magnets and put out a great spark but the new JHs are 4 rare earth magnets and the out put of the spark is even more stronger and the faster it spins the bigger the spark.
Most troubles with the maggies mounted behind the motor is heat from the motor they run very hot behind there and thats where a lot of trouble with the maggies begin or become un reliable as well the extra chain you have to run in the timming cover, but with it sticking off the side the JH is running in full flow of air around them and run a lot cooler and in the long run more reliable and it runs straight off the cam, yes its more vanable sticking out the side but thats the risk we all take when we ride our bikes, the idea is to stay up right and not come off, but in racing that becomes a bit more harder.
In 9 years of running one on my stock Triumph I never had any problems at all with the old JH with the 2 rare earth magnets and always started first kick evey time and clocked up 250,000kms with it with only doing general maintenance on it, the new JH with 4 rare earth magnet has been on my hot Norton for over 7 years now has just over 30,000 miles on it and also starts on first kick every time and only a half swing on the kicker after its been fired up for the day and so far have not touched it.
I have had no problems dealing with JH and have had parts sent over to me from them in a few days after ordering parts when I wore out my top cover sliding down the road as well I got a tune up kit which comes with new points, condenser and new plug leads and caps, the tune up kit is still stitting on the workshop bench.
Most folks on here are going to tell you to use a EI set up on your race bike, but after 43 years with my Norton and my share of failures from points to EIs and flat batteries to being left stranded a 100 miles from home with a failed black box, the JHs are so simple, easy to work on and very low maintenanceand parts are cheap if you need them.
With the amount of work I have done on my motor and with the carbies tuned right the JH work so well with all the other bits and peices I have done to make my hot rod work so well.
Be good to know how many problems folks have had with their JHs that are mounted behind the motor compared to any problems mounted on the side other than falling off, be interesting to know, I know a few lads running JH off the side and have always talked to other at bike shows who run them and so far have never heard of them having any problems at all running them or any failures of the JH.
But if your prone to falling off all the time then I proberly wouldn't go the JH way, but of course everyone knows my opinion about the Joe Hunt maggies and set up right and tuned right you will have one of the best ignition systems around, but most people who say to stick to EI are the ones who have never used a well set up JH before and of course the old debate "its got no advance" I laugh everytime I hear that one.
Remember there are the old JHs and there are the newer JHs, the newer ones are so much better than the older ones and you will get longer life out of your spark plugs as well, they run so much cleaner.
Of course it will always be up to you what ever way you go with your race bike and we all have our own opinions in whats best and for what best for me and loving it is the JH way it works so well for my Norton and from zero revs to full revs it will keep sparking till things go bang if you over rev your motor.

Ashley

I run my Atlas hard in hot weather and have never had a heat problem with my behind the cylinders mag. I've never heard of a heat problem from any of my many customers who are using a behind the cylinders mag.

What is this rumored heat problem about? Is it just BS or is there a specific component that fails at a certain heat range? Who has had a modern JH mag fail from heat and acually pinpointed the problem? I can't get mine to fail from overheating no matter how hot I run it (idling at traffic lights or racing to the nearest air conditioning in 110+F heat in hellish Fresno Calif).

Here's what I know that can fail:
Coils and condensers same as any coil or condenser that can fail from broken internal wiring.
A few early 2011 JH mags had 4 large magnets that were too powerful and could burn points but this was corrected.

If you're concerned about heat - Search this forum for ignition failures and you'll find numerous reports of EI overheating (melted potting compound, warranty exchanges etc).

Most Lucas magnetos are not rotating magnet, so you cannot easily change the coil or the capacitor. In the olden days I took my bike to several race meetings where it started to miss almost immediately, even though I'd had the magneto overhauled by the 'experts'. When that happened I usually lost my entry fees and travel costs. A Lucas SR magneto off a stationary motor is a good option. The one on original Manx Nortons is rotating magnet.

jseng1 said:

I run my Atlas hard in hot weather and have never had a heat problem with my behind the cylinders mag. I've never heard of a heat problem from any of my many customers who are using a behind the cylinders mag.

What is this rumored heat problem about? Is it just BS or is there a specific component that fails at a certain heat range? Who has had a modern JH mag fail from heat and acually pinpointed the problem? I can't get mine to fail from overheating no matter how hot I run it (idling at traffic lights or racing to the nearest air conditioning in 110+F heat in hellish Fresno Calif).

Here's what I know that can fail:
Coils and condensers same as any coil or condenser that can fail from broken internal wiring.
A few early 2011 JH mags had 4 large magnets that were too powerful and could burn points but this was corrected.

If you're concerned about heat - Search this forum for ignition failures and you'll find numerous reports of EI overheating (melted potting compound, warranty exchanges etc).

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Jim in all the people I have talked to that run JH maggies and there have been many in the last 20 years of running JHs not one had any complains about their JHs, but in the last 7 years since I have been running my JH on my Norton and numrous threads on this subject of JH maggies on this forum it all seems to be negative with most people on this site and because I run one that sticks out the side the flack that I get because it sticks out the side and of course the crap about "it looks ugly sticking out the side" myself think its a work of art and because I know it works so well I luv it sticking out the side sitting proudly off the end of the cam sitting in the cool breeze.
I have only come across one owner who had the JH mounted behine the motor but all the others I have talked to all had the side mounted JH and most were Triumph owners with the older JHs.
Many years ago Morris maggies made a maggie for the older triumphs that mounted in front of the motor and the drive for the maggie ran off the taco drive, the maggie was well protected but not sure if they sold many as I never seen one.
But really the most problems people have had running JHs behind the motor usualy had a very old JH and like anything meckinical things do wear out and things do need to be replaced over time as well a lot of folks are cheap and will only spend the money needed and most go EI because they are cheap but a JH will cost just over $800 delived and a lot of folks won't spend that much on a reliable system.
My Norton has always copped a hard life from new I ride and push my bike hard where ever I ride and how I ride and so far the JH has been one of the best things I have ever put on my Norton and I have done a lot of changes to it in the last 43 years and we suffer very hot summers as well.
I am a true believer of the Joe Hunts and will always talk highly of them as really in 20 years of running JHs I have never had any problems with them except for a few lay downs but they were not my fault, bloody cars they should be band lol.

Ashley

A track bike? Is saving some weight here and there interesting?

The first Joe Hunts I saw way back when were the Triumph variety as you described and I always thought they looked great and the bikes they were on were so clean and tricked out that I assumed the mag was the desirable way to go. Also think they look very interesting even if they hang out the side. After having an EI fail on me at the worst time and now having a late model JH mag running for years that starts easier than any other ignition I've had - I'll probably stay with it. I'll admit that a good EI is more precise at high RPM and may get 2 more HP but I can still rev my mag cleanly up to 8000+ and the simplicity, reliability and old school funkiness of it makes me feel good. Personally I think the photo below looks great - maybe even a little bad ass. And I've heard similar comments from others.



As for racers - you can forget about the total loss hassle and the embarrassment/disappointment of sitting quiet on the grid with a dead battery.

A friend was handed this tank-shifter to ride, but issues with the mag kept it from running clean enough to race. Dyno runs revealed a bad condenser in the mag, but apparently the correct part wasn't available, so a substitute was piggybacked on outside the mag case. When that one failed, another one was subbed, but the same result with the motor breaking up under load on acceleration.

The one failure I had with my mag was the condenser. The condenser needs to be matched to the mag. There aren't many components in a mag and the condenser is one thing that can act up and still allow the mag to work (but badly). You've got to have the right condenser and its good practice to replace it occasionally. I set mine up with a bullet connector in the wire so its easy to replace.

I always had trouble with Lucas magnetos until I bought the rotating magnet variety where the condenser is mounted externally. I those such as the Lucas wader, the condenser is internal and it is a major operation to replace it. On my Triton, the magneto was a Lucas SR4 and I ran two leads to each spark plug. If I was going to change the ignition system on my Commando motor, I think I would buy a cheap second-hand system off a VT750 Honda and play with a hall-effect triggering system. My friend did it with a Ducati 750 Sport and it worked extremely well.

Hi, found a reliable spark system yet? You might want to try Bike sparks which used to be attached to Bike techniques , of North St Mews which I used over 30 years ago, so it may be a bit old news now, the person you want is Andy. If you phone them up, ask if the building opposite is still used by Bike techniques, as they had the whole of the first floor, with their Motoliner frame straighting jig.

I would love to know if they are still going……………..

https://www.allinlondon.co.uk/directory/1079/28830.php


They were the one who sorted out the sparks for the Kawasaki 5 cylinder;

http://www.bikebound.com/2017/07/11/kawasaki-kh500-millyard-special/

You have me thinking. That JH on the Triumph motor in the photo doesn't look so bad. With methanol fuel - without losing power, there is much more flexibility allowed in the balance between jetting, ignition advance and comp. ratio. And a lot of adjustment can be achieved by varying the taper on the carb needles. Petrol is a bit different - getting that right is much more critical. With the Commando motor fitting a magneto in the old position behind the motor, is a major task.

With total loss ignition system, playing with batteries is always a pain. Once you put the acid in the battery, you need to keep it on trickle charge. It becomes one more reason to avoid starting the bike's motor. A JH magneto might not cost much more than a good lithium battery and programmable ignition system. And would probably be just as effective. I don't doubt that a programmable ignition system might give a better result, but so might developing a stronger right wrist.
Is it possible to get a JH which fires both plugs simultaneously ?

acotrel said:

Is it possible to get a JH which fires both plugs simultaneously ?

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Why would you want to fire both cylinders simultaneously in a Commando? Just curious.

Ken

When I first fitted a older JH maggie to my Triumph back in 82 before I put it on I had it on the bench and my mate asked how good the spark is, this maggie was only just fully rebuilt and not used before I got it, we held the spark lead away from the maggie case and turned it slowly by hand, man what a spark it was like a small lighting bolt and it made a big cracking sound, we did this a few times and holding the lead further away but the spark kept jumping and cracking sound was still doing it, my mate and myself was very impress, then my mate got zapped by it, he jumped about 2' off the ground in great pain and he went very quite for sometime after and said he felt it go through his whole body.
When we installed the newer JH to the Norton the same mate was there to see it fire up I asked if he like to grab hold of the lead to test it out seeing he was experience with the older one, he didn't see the funny side of it and said no way.
Would a EI do that???
Al I am not sure why you would like to have a JH fire both cylinders at the same time.
Compared to the old Lucas maggies, the JHs are so simple in design, easy to work on and replacement parts are cheap if you ever need parts, they are well built and will with stand a lot of punishment and the best part is ease of starting 1/2 a swing on the kicker and it will fire up and everytime I pull the plugs they are always clean like they have just been put in even after 25,000 mile on the plugs.
Since buying my new 1200 Thruxton 12 months ago all my other bikes have just been sitting in the corner of my shed, the other day I pulled the Norton out to install a small battery so I got a horn and brighter brake light and a brighter head light if I get caught out at night, putting fresh fuel in the tank drained the oil out of the sump and with one big kick she fired into life, not bad for sitting for 12 months untouched and it ran the same as it did when I last rode it.

Ashley

Joe Hunt mags are descendants of Fairbanks Morse magnetos of years gone by. The FM mags were on machinery I used during my trade years, these machines using single cylinder Wisconsin engines. They were always very easy to start.
I had worked on a number of oddball engines as a kid such old military engines, lawnmowers, a few Honda 55's, etc.. When my friend's younger brother bought a '60's custom hard-tail Triumph chopper, he needed help. It was basket case 650 that came with a Webco 800cc big bore kit--and a Joe Hunt mag! He had no idea how to put it together, so he asked me to build it. I was 17 at the time and could equate this project to taking on a basket case Rolls Royce Merlin engine. Way above my experience level...

It went together well, started easily, but it was quickly apparent the crank was not balanced for the big-bore kit. It looked really cool, the shorty pipes sounded bitchin, but the beast was an agony to ride. The Joe Hunt mag worked a treat until on one ride, the ignition just vanished as the mag was seen bouncing along the road and off to the shoulder. Loctite is the moral of this post!

Best,
~998cc