Joe Hunt magneto

Neodemium high temp magnets are available for up to 300 deg but I don't know what's in the JH. Regulan neodemium magnets are good to 175 deg. I've had easy starting after 10+ years with the mag behind the cylinders in the hot climate where I live. No kickback with the Atlas automatic advance at 28 deg. For a timing cover mounted JH Commando mag you can get a retard lever kit (available only from Morris magnetos) to avoid starting kickback as shown in the photo.

One can expect oil temps (and timing case temp) to reach 180F under normal cruise power and peak to 200F with sustained full power throttle. Since this is over the 175F limit for the magnets, an insulating gasket may be in order. An oil cooler can be expected to lower oil temps by 30 to 40 degrees F.

Slick

Schwany said:

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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It's 3000 RPM

Depending on the accuracy of the thermometer I have in the oil tank, the oil temp is usually 180 - 200 degrees.
Worked on the mag problem today. The chain needed a small amount of tightening. Trying to loosen the nuts and give the mag a nudge took forever. Next, I put new terminals on the sparkplug leads and made sure I had the best possible. The bike fired up immediately with no kickback..twice. The timing mark is now stable. Not sure which one is the cure but the problem now seems to be behind me.

You

seattle##gs said:

Depending on the accuracy of the thermometer I have in the oil tank, the oil temp is usually 180 - 200 degrees.
Worked on the mag problem today. The chain needed a small amount of tightening. Trying to loosen the nuts and give the mag a nudge took forever. Next, I put new terminals on the sparkplug leads and made sure I had the best possible. The bike fired up immediately with no kickback..twice. The timing mark is now stable. Not sure which one is the cure but the problem now seems to be behind me

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You need a 7/16" crow's foot wrench to loosen the mag nuts. Start with 1/4" nuts then drill and rethread them to fit the studs on the timing case. The 5/16" nuts are too big and a problem when wrenching.

Timing light is not always steady with a magneto - too much loose energy flying around.

With the rear mounted JH you run an extra chain to the timing gear as well the cam chain if one or the other is loose it will put your settings out and make your timing flicker, I am lucky running mine out the side directly off the cam I run an auto timing chain adjuster and have never had a problem with my timing it's been set and forget for me, one of the reasons I don't touch my JH much except for a check under the front cover every time I do a service on my Norton, it's also wise to have a tune up kit handy when time to replace point and as I have said before is wise to replace the capacitor every few years.
We all have our preference to where we mount the JHs, me I love mine running off the timing case, everyone makes a big fuss about retarding the maggie to start without kick back, but I have had no problems with kick back from running timing case mount JHs on both Triumph or Norton, they fire up every time on first kick at full advance because they produce such a big spark.
If you go back over 12 years there is a video of my Norton after a major rebuild and install of my new JH maggie as well new PWK carbs fitted, the first kick it fired straight up even with the new carbs not tuned in.
No matter where the JHs are mounted I just love them for the simplify and easy maintenance and great reliability, I have a 1960 Manxman project bike it's an ex race bike and has a Lucas competition mag that is spinning by hand a good spark but if I finish this build off and the Lucas ever failed I would replace with a new JH instead of rebuild of the Lucas mag.

Ashley

Hi all,
Am I missing something? What is the point of an external magneto? This is a serious question.
Im sure the JH magneto provides an excellent spark but why would you ever want a large lump of aluminium, iron and copper hanging off the side of your bike. It must be incredibly vulnerable to being written off, along with the timing cover and potentially internal damage from even the most minor mishap.
Do the magnetos have an advance mechanism?
What does the magneto do that a good electronic ignition doesn’t do? All my bikes have either a Rita or a Boyer ignition which have not given any trouble for decades. They are hidden and are not visible externally (the Lucas Rita does have a different points cover). If I was replacing them I think I would go for a Trispark.
I look at the ignition modules on small motors like chainsaws etc which are the size of a thimble and provide a bight blue spark and wonder why you would want a JH magneto.
Regards
Alan

Alan L said:

Hi all,
Am I missing something? What is the point of an external magneto? This is a serious question.
Im sure the JH magneto provides an excellent spark but why would you ever want a large lump of aluminium, iron and copper hanging off the side of your bike. It must be incredibly vulnerable to being written off, along with the timing cover and potentially internal damage from even the most minor mishap.
Do the magnetos have an advance mechanism?
What does the magneto do that a good electronic ignition doesn’t do? All my bikes have either a Rita or a Boyer ignition which have not given any trouble for decades. They are hidden and are not visible externally (the Lucas Rita does have a different points cover). If I was replacing them I think I would go for a Trispark.
I look at the ignition modules on small motors like chainsaws etc which are the size of a thimble and provide a bight blue spark and wonder why you would want a JH magneto.
Regards
Alan

Click to expand...

I went down that road some years ago, I used a system on a racing bike that was designed for model aircraft. I learnt a lot from this.

Chainsaws have tiny combustion chambers. Tiny combustion chambers only need tiny sparks. Big (and by modern standards) inefficient combustion chambers benefit from big, fat, long duration sparks.

There is more benefit to be had from big fat sparks in old skool engines like ours than there is from playing with ign timing and advance curves etc, in my experience at least.

I say.. I say, what we need here are some head-to-head dyno tests! Same bike, same engine, using different types of ignition (magneto versus coils & electronic ignition) to light the far!

concours said:

I say.. I say, what we need here are some head-to-head dyno tests! Same bike, same engine, using different types of ignition to light the far!

Click to expand...

I had a BSA R3 heavily modified 1000cc, back to back on the dyno replacing a Boyer with a TRI spark firebox (think thats what it was called) and saw a 5 BHP increase.

The Boyer was a wasted spark using 4 volt coils. The Firebox was a dedicated spark using 12v high output Dyna coils.

Spent a whole day trying to improve further with different ign settings and programming of the advance curve and discovered that relatively large changes made no difference. And standard timing with the fastest advance was good as it got.

Had similar results on Triumph and Weslake twins when changing from fancy lightweight model aircraft igns to a ‘red top’ Interspan, this is the version with the biggest fattest spark, originally designed for methanol.

Its not just the outright HP that benefits, easier starting and smoother curves too.

Hence on the current build I’m gonna play with a high output Joe Hunt mag.

Fast Eddie said:

I had a BSA R3 heavily modified 1000cc, back to back on the dyno replacing a Boyer with a TRI spark firebox (think thats what it was called) and saw a 5 BHP increase.

The Boyer was a wasted spark using 4 volt coils. The Firebox was a dedicated spark using 12v high output Dyna coils.

Spent a whole day trying to improve further with different ign settings and programming of the advance curve and discovered that relatively large changes made no difference. And standard timing with the fastest advance was good as it got.

Had similar results on Triumph and Weslake twins when changing from fancy lightweight model aircraft igns to a ‘red top’ Interspan, this is the version with the biggest fastest spark, originally designed for methanol.

Its not just the outright HP that benefits, easier starting and smoother curves too.

Hence on the current build I’m gonna play with a high output Joe Hunt mag.

Click to expand...

Great info right there

Fast Eddie said:

I had a BSA R3 heavily modified 1000cc, back to back on the dyno replacing a Boyer with a TRI spark firebox (think thats what it was called) and saw a 5 BHP increase.

The Boyer was a wasted spark using 4 volt coils. The Firebox was a dedicated spark using 12v high output Dyna coils.

Spent a whole day trying to improve further with different ign settings and programming of the advance curve and discovered that relatively large changes made no difference. And standard timing with the fastest advance was good as it got.

Had similar results on Triumph and Weslake twins when changing from fancy lightweight model aircraft igns to a ‘red top’ Interspan, this is the version with the biggest fastest spark, originally designed for methanol.

Its not just the outright HP that benefits, easier starting and smoother curves too.

Hence on the current build I’m gonna play with a high output Joe Hunt mag.

Click to expand...

I would offer the COIL makes a huge difference in spark.

"model aircraft ignition" is there sarcasm there, based on some history, that I am missing?

Please tell me about smoother curves, I'm ALWAYS interested in that....

Alan L said:

Hi all,
Am I missing something? What is the point of an external magneto? This is a serious question.
Im sure the JH magneto provides an excellent spark but why would you ever want a large lump of aluminium, iron and copper hanging off the side of your bike. It must be incredibly vulnerable to being written off, along with the timing cover and potentially internal damage from even the most minor mishap.
Do the magnetos have an advance mechanism?
What does the magneto do that a good electronic ignition doesn’t do? All my bikes have either a Rita or a Boyer ignition which have not given any trouble for decades. They are hidden and are not visible externally (the Lucas Rita does have a different points cover). If I was replacing them I think I would go for a Trispark.
I look at the ignition modules on small motors like chainsaws etc which are the size of a thimble and provide a bight blue spark and wonder why you would want a JH magneto.
Regards
Alan

Click to expand...

Amen Brother, TESTIFY!

concours said:

I would offer the COIL makes a huge difference in spark.

"model aircraft ignition" is there sarcasm there, based on some history, that I am missing?

Please tell me about smoother curves, I'm ALWAYS interested in that....

Click to expand...

No sarcasm anywhere.
Yes, I agree, the coils made the bigger spark which made the bigger bang.
But I’d offer that, all else being equal, 12v high output coils will out perform 4 volt coils of any type, I don’t even think you could (can?) get high output 4v coils. And the ign being a wasted spark or not dictates this. And this was the case on the R3 as the Boyer was a wasted spark and the programmable Tri Spark was not. Hence it simply allowed for more powerful coils.

Dyno curves are often not smooth as the Dyno picks up on micro missfires etc that we wouldn’t detect per se. There was simply a smoother more solid line, indicating a more reliable spark, which indicates a better burn.

The model aircraft ign was called Runtronic. I don’t even know if they’re still in existence. Dave Degens used it successfully on his 8 valve 500, but that had a much smaller combustion chamber and tight squish and was over 12:1 CR. It weighed almost nothing.

The same spark just didn’t seem enough for a 900 twin however.

I am a confirmed Tri Spark fan, so fear not, if the mag doesn’t full-fill the requirements on my current project, it’ll be gone! But the motor has big bores and big combustion chambers to ignite, so I’m hopeful it’ll work well and support my batteryless / chargeless set up.

Disclaimer:
I make ZERO claims re electrickery knowledge. I’m only going by personal empirical evidence / experimentation / blagging.

'Hence on the current build I’m gonna play with a high output Joe Hunt mag.'

Pun intended???

Fast Eddie said:

No sarcasm anywhere.
Yes, I agree, the coils made the bigger spark which made the bigger bang.
But I’d offer that, all else being equal, 12v high output coils will out perform 4 volt coils of any type, I don’t even think you could (can?) get high output 4v coils. And the ign being a wasted spark or not dictates this. And this was the case on the R3 as the Boyer was a wasted spark and the programmable Tri Spark was not. Hence it simply allowed for more powerful coils.

Dyno curves are often not smooth as the Dyno picks up on micro missfires etc that we wouldn’t detect per se. There was simply a smoother more solid line, indicating a more reliable spark, which indicates a better burn.

The model aircraft ign was called Runtronic. I don’t even know if they’re still in existence. Dave Degens used it successfully on his 8 valve 500, but that had a much smaller combustion chamber and tight squish and was over 12:1 CR. It weighed almost nothing.

The same spark just didn’t seem enough for a 900 twin however.

I am a confirmed Tri Spark fan, so fear not, if the mag doesn’t full-fill the requirements on my current project, it’ll be gone! But the motor has big bores and big combustion chambers to ignite, so I’m hopeful it’ll work well and support my batteryless / chargeless set up.

Disclaimer:
I make ZERO claims re electrickery knowledge. I’m only going by personal empirical evidence / experimentation / blagging.

Click to expand...

I have elektronik Saches on my t160 with three 12v red high power Lucas coils
Iridium spark plugs
The bike is always on the button and revs like a banshee
I have the advance set on std curve,never seen a reason to change it
Cheers

Fast Eddie said:

The same spark just didn’t seem enough for a 900 twin however.

I am a confirmed Tri Spark fan, so fear not, if the mag doesn’t full-fill the requirements on my current project, it’ll be gone! But the motor has big bores and big combustion chambers to ignite, so I’m hopeful it’ll work well and support my batteryless / chargeless set up.

Click to expand...

Are you still thinking about hanging the JH ignition lump off the side? (Insert barf emoji here)

Too bad somebody is not making a really small alternator. TriSpark with a wallet sized LiFePO4 battery, a silicon reg/rect, and a good epoxy filled dual coil would do the job if a small light weight alternator was available. All kind of obvious, but anything would be better than hanging a magneto off the side of a track bike. To me anyway.

Schwany said:

Are you still thinking about hanging the JH ignition lump off the side? (Insert barf emoji here)

Click to expand...

No I’m not thinking about it anymore… I’m doing it !

But I don’t think it’s the kinda bike where something like that is gonna detract from the aesthetics…

Alan L said:

Hi all,
Am I missing something? What is the point of an external magneto? This is a serious question.
Im sure the JH magneto provides an excellent spark but why would you ever want a large lump of aluminium, iron and copper hanging off the side of your bike. It must be incredibly vulnerable to being written off, along with the timing cover and potentially internal damage from even the most minor mishap.
Do the magnetos have an advance mechanism?

Click to expand...

The mag also requires no battery and is completely separate from any other electrical components. The (big, fat, long lasting) spark is created from the rotation of the mag (with no external components needed), so it's very reliable. Short of a kill switch, the only wiring you need is to the plugs. You can run an advance mechanism inside the timing chest (when not run off the cam) that has bob weights that advance the timing via centrifugal force once everything starts spinning. Dead simple for dummies like me.

Any weight you might "save" on a road going bike with EI is offset with the weight of the other electrical components. Batteries are certainly getting lighter, so the weight difference is getting smaller, but the complexity of the ignition system is far greater due to the draw needed for the EI at kickover. Mags have no need for any of that. EI is certainly more precise, but our bikes are generally far from the ability to match and take advantage of that precision.

All the above is for ignition systems. An alternator or dynamo is still needed for lighting or other accessories. I've wondered myself about a more minimal alternator or dynamo, with head and tailights drawing essentially nothing with the advent of high output LED lighting. A half-width rotor and stator could certainly create enough juice, couldn't it? Hmmmm...

I agree about the aesthetic challenges of a timing cover mounted mag though. Cool breeze and all that notwithstanding.

Fast Eddie said:

No I’m not thinking about it anymore… I’m doing it !

But I don’t think it’s the kinda bike where something like that is gonna detract from the aesthetics…

Click to expand...

Alrighty then. Certainly, easier that putting one behind the cylinders. Very fiddly install there. I've got all the parts to make it possible, but no interest in ever using one again.

Avoid doing a low side in a right hander. Probably not likely to happen on a track day bike unless the motor or rear hub locks up.