Joe Hunt magneto

seattle##gs

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JH recommends setting their mag at 28 degrees BTDC. Most electronic ignitions use 30 - 32 degrees. Any experience with this difference? I installed a JH mag the other day and it wants to kick back. I timed it to 30 degrees at 2000 rpm. There is a little chatter while timing...the timing mark is not dead still.
 
Set the timing to whatever it takes for best running.
I surmise you have the timing case mounted JH. If so, you can expect more kickback with greater advance, as there is no starting retard available with timing case mounted JH,
With that in mind, 28 deg is least kickback.

Slick
 
I static time my JH at 28 degrees and start it as its pretty close, I don't have a timing light and if it kick backs I just retard it ever so slightly till no kick back, have you set your plugs at 18 thou as recommended, my JH work great from low revs right as far as I want it to rev without any hesitation + my Norton runs better with Champion N7YC plugs with the JH the plugs are always clean looking without any wear to them even after over 12 years running the JH, I have new plugs but its running sweet and starts on first kick every time, I was running PWK crabs but now have gone back to my old Amals, haven't fired it up yet doing a few other things to my Norton but life keeps getting in my way.

Ashley
 
texasSlick said:
Set the timing to whatever it takes for best running.
I surmise you have the timing case mounted JH. If so, you can expect more kickback with greater advance, as there is no starting retard available with timing case mounted JH,
With that in mind, 28 deg is least kickback.

Slick
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I been running 2 JH mags that ran off the timing case mount one off my old Triumph and now my Norton set right they no need to be retarded to fire up first kick every time, first kick for the day need a good solid first kick once fired up for the day it will fire up on 1/2 a swing on the kicker, in fact I have no troubles sitting on my seat to kick it to life with a lazy kick.
I don't know why everyone makes a fuss about retarding a JH maggie to start them as really they fire up first kick every time without retarding them if they are set up right, my JH has been on my Norton for over 12 years now and to be honest I haven't touched it, only pulling the front cover off when I do an oil change just to check the point and put a few drops of STP on the felt pad for the points cam.
These new JHs with the 4 rare earth magnets produces one of the biggest sparks I have ever seen and the spark will jump a distant if your plug lead pops off the front maggie cover as it happened to me once while riding.

Ashley
 
seattle##gs said:
JH recommends setting their mag at 28 degrees BTDC. Most electronic ignitions use 30 - 32 degrees. Any experience with this difference? I installed a JH mag the other day and it wants to kick back. I timed it to 30 degrees at 2000 rpm. There is a little chatter while timing...the timing mark is not dead still.
Click to expand...
Could your timing chain be a bit loose and needs adjusting to cause your timing mark not be dead still, I been running an auto timing chain adjuster for over 30 years now, a loose chain or worn Rota centre will cause the marks to not be dead still.
 
The engine needs a variable ignition advance. The tractor engine magneto, with NO PROVISION for advance, is a folly.
 
I installed the mag 2 days ago. The bike is about an hour away. I forgot to bring the AN tool for holding the idler shaft so I could not tighten the chain properly. Will do this tomorrow also return to 28 degrees.
Previously the mag was running great but slowly developed a starting problem. JH said it lost a lot of magnetism and was only putting out 1.5 amp...now it puts out 4 amps. JH claims the loss of magnetism is normal and should be remagnetized every 2-3 years which doesn't sound right.
This fits an Atlas, bolts on to the rear of the timing case.
 
Mine hasn't lost any power at all still fires up first kick every time, my old Triumph JH maggie I done 250k km with that JH without any work done on it and was still on the bike when I sold it.
 
Loss of magnetism, being claimed normal, makes no sense to me.
So, then, you have a flange mounted JH. The Lucas AAU fits the JH shaft taper and if fitted will retard the timing from 28 degrees to 4 degrees. No kickback should occur with that combination.
Having an AAU fitted will allow you to set the timing up to 32 deg BTDC without a kickback problem. I find with 9:1 CR, and modern fuels, my Atlas seems to like 30 deg BTDC.

From your post, Reply #8 above, I surmise the JH was on the bike for some time before your first post creating this thread. How long? It has been rumored that a flange mounted JH behind the cylinders will lose magnetism from the heat there. Jim Schmidt has told me he does not know how that rumor got started, and has a JH on his Atlas behind the cylinders and routinely runs in 100+ F temperatures. Regardless, your JH may have suffered from "heat stroke". Perhaps the rumor is true, and JH KNOWS this ..... that may explain why they say the magnetism needs a bump every 2 to 3 years.

Ashman tells us his Timing cover mounted JH has been stable for years. This would be an older JH. The newer models with the 4 rare earth super magnets may not be as stable.
In any event, Ashmans timing cover mount should not be compared to a flange mount behind the cylinders.
Slick
 
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Magnets do lose their magnetism under heat, and rare earth neodymium magnets do seem to be more susceptible to it. Max operating temperature is a variable in magnet specification and neodymiums are the lowest temp rating.

If behind the cylinders is hot enough to do it, I don't know, but I have an old JH mag that could probably use a new capacitor after 30 years, but still runs fine back there in the heat. While seemingly not necessary, the retard from the AAU seems to make life easier.

Would be bummer if you had to get the new mags bumped up every few years. They're a right pain in the ass to remove and replace with that buried nut. The whole allure of them is the fit-and-forget aspect.

For whatever that's all worth.
 
texasSlick said:
Ashman tells us his Timing cover mounted JH has been stable for years. This would be an older JH. The newer models with the 4 rare earth super magnets may not be as stable.
In any event, Ashmans timing cover mount should not be compared to a flange mount behind the cylinders.
Slick
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Slick my JH on my Norton is the 4 rare earth super magnets and hanging off the timing cover hang out in the cool breeze and runs cool, some may say the heat don't worry them behind the motor and I know lots of the old Lucas mags did suffer some heat problems and whether they do with the JHs mounted behind the motor, I wouldn't know as I always had a timing case mount JHs, maybe that is why they might lose magnetism caused from heat, who knows.
My JH is set at 28 degree full advance when set static, will fire up first kick from doing static timing but if any sign of kick back I just retard it ever so slightly till no kick back as I don't use a timing light, once set right and in over 12 years on my Norton and well over 35K miles on it, it has never kicked back when kicking it, as I say it starts first kick every time and most of the time it fires up even before I get 1/2 way through the kick and that's at full advance.
One thing I know the capacitor should be replaced every few years, JH sell the tune up kit for about $40 comes with new points, capacitor and new copper core plug leads, I have a tune up kit but so far haven't needed to use it yet, while its running good and starting first kick I leave things alone, another thing never clean the points with a points file, if you do the point's will wear out real quick, I just clean mine with a bit of Metho and a bit of rag if it needs cleaning, but so far haven't touch them same as the spark plugs, running good leave them alone, plugs seem to run very clean with a hot spark from the JH.

Joe Hunt magneto


As you can see in this pic my JH hasn't been touched for a very long time, the timing allen head bolts haven't been touched in over 12 years since it's been mounted and set, I also run a bridge on the plug leads near the cover, this stops the plug lead from popping out off the cover and I only pull the cover off just to check the point's and lube the felt pad for the point's cam, but that has been over 12 months since I done that, I know I have been a bit slack lately.
Joe Hunt magneto


This is one of my mate's old Triumph Bobber the JH on it has been on that bike for over 25 years now and he has only just changed the points, capacitor and plug leads for the first time in he can't remember how long ago, this is the older JH 2 rare earth maggie but it's not a long distant rider like my old Norton.
But hanging out in the breeze the JHs seem to be very reliable and happy hanging there.
Joe Hunt magneto

This is a pic of my old 1981 Triumph 650 Thunderbird with my traveling bread box fuel tank with my old 2 rare earth JH I done 250k km on that bike with that JH maggie and only done general maintenance to the maggie in all those km's, that was the most reliable bike I ever owned and still regret selling it to this day, I rode the wheels off that bike.

Ashley
 
seattle##gs said:
Is it possible to put a heat shield between cylinders and mag?
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Perhaps a turning vane mounted near the cylinder base might get some cool air flow back there.

An insulated gasket between timing case and magneto flange may actually be counter productive. If the air temp behind the cylinders is higher than the oil temperature, which is what the timing case is expected to be, then the timing case against the flange is actually a heat sink.

Don't waste your time with a funnel mounted into the on coming wind, with a tube leading to the mag .... you will not get any significant air flow thru the tube, regardless of funnel mouth diameter.

Please keep us informed of the outcome of this issue. I have a keen interest as I am considering replacing my Lucas K2FC with a behind the cylinder JH. My leg strength is failing me in my advanced years, and kicking over the old Atlas is becoming problematic.

Slick
 
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concours said:
The engine needs a variable ignition advance. The tractor engine magneto, with NO PROVISION for advance, is a folly.
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ashman said:
Have you used a JH before.
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It doesn't matter what sort of ignition is employed. If there is no provision to retard the timing automatically at start up, setting timing to start without manually retarding the spark will result in less than optimal ignition timing at higher RPM. I've watched guys with pre-66 Hogs set the timing so they could start the engine without manually retarding the timing. This was one of several reasons that Panheads were thought to have less power potential than Shovelhesds. That assumption was simply not true. Running retarded timing along with the restrictive 1 1/2" intake manifold was strangling the HP potential.
 
texasSlick said:
@t ingermanson
What is the temperature spec for neodymium magnets.

@all
Does anyone know, or has measured the air temp behind the cylinders?

Slick
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A quick check at McMaster gives a max temp spec of some at 175F and some at 200F. I use magnets all the time to hold little doodads on when welding them on to a larger base. The little horseshoe magnets last a few years before they stop working well enough to hold things in place. I bought some neodymiums thinking I was a smart guy and the first one I used lasted for one use.

It would be hard to imagine the air temp getting high enough to roach the little guys in one go, but it's also hard to imagine it not sitting at 150F back there regularly for long periods.
 
Kick harder and don't worry about the magneto being behind the cylinders. I would listen to JH tech support on timing. 28 degrees is plenty of all in advance if kicking it over without any kick back is the goal. TriSpark EI recommends 29 degrees all in at 2500RPM. Unless its 3000RPM. I can't remember.
 
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