Lets talk magnetos.

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Would it be easier just to use an Atlas dual timing chain/gear setup and just hog out a hole and drill and tap for the mount bolts in the back of the 850 case?
 
Danno said:
Would it be easier just to use an Atlas dual timing chain/gear setup and just hog out a hole and drill and tap for the mount bolts in the back of the 850 case?
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Dunno about the 850, but according to my eyeballs, the 750 intermediate gear and sprocket is same as the Atlas, except for lacking the mag drive sprocket, so I would think a swap could be easily done.

Adjustment of the mag chain is accomplished by the three mounting studs (5/16" dia.) having a 1/4" dia. waist where they pass thru the magneto flange. Drilling the 3 holes for the mounting studs, precisely where needed would be the challenge.

Best to wait for someone who has actually tried this, to advise, before doing it.

BTW ..... if it proves doable, use a bolt, rather than a stud, for the lower mount. This might require a spotface for the hex head to clear the mag drive chain. If you have ever removed the nut from the lower stud on an early Atlas, you will understand why I suggest the bolt.

Slick
 
It's been so long, but it seems like the chain tensioning was like the primary, so super-precise location of the mag mounting hardware shouldn't be necessary as there has to be some play to tension the chain properly? Like the bottom stud was the pivot and the other two had elongated holes in the mag base.
 
Another ? For years, the Commando timing side castings still had an opening for the rear ignition drive, with a plate bolted over the opening until at some point, the opening was eliminated. Do those tapped mounting holes correspond to the flange of the K2F? If so, early Commando bottom ends would easily convert rather than using Atlas cases.
 
Danno said:
It's been so long, but it seems like the chain tensioning was like the primary, so super-precise location of the mag mounting hardware shouldn't be necessary as there has to be some play to tension the chain properly? Like the bottom stud was the pivot and the other two had elongated holes in the mag base.
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Not on my Atlas! The tensioning is as I describe above. The holes in the K2F flange are not elongated, but are of diameter to go over the 5/16" studs. There is not much lateral adjustment, but enough to loosen for removal of the AAU, and enough to tighten beyond "too tight". The magneto drive chain is lightly loaded and well lubricated, so adjustment for wear is not a factor.

Re: Your next post.

I do not know for sure, but it stands to reason, from the standpoint of mass production machine tooling, that the layout of the three holes in early Commandos, would have been the same as pre-Commando models.

Slick
 
texasSlick said:
Not on my Atlas! The tensioning is as I describe above. The holes in the K2F flange are not elongated, but are of diameter to go over the 5/16" studs. There is not much lateral adjustment, but enough to loosen for removal of the AAU, and enough to tighten beyond "too tight". The magneto drive chain is lightly loaded and well lubricated, so adjustment for wear is not a factor.

Re: Your next post.

I do not know for sure, but it stands to reason, from the standpoint of mass production machine tooling, that the layout of the three holes in early Commandos, would have been the same as pre-Commando models.

Slick
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the problem ,though not insurmountable, that I see is that of a heat shield. not much of a problem with the ktf , but Jim in an earlier post made clear that modern magnets are liable to failure. The answer is a thick tufnol gasket between the magneto body and the engine case. but then that will throw the chains out of alignment
 
oldmikew said:
the problem ,though not insurmountable, that I see is that of a heat shield. not much of a problem with the ktf , but Jim in an earlier post made clear that modern magnets are liable to failure. The answer is a thick tufnol gasket between the magneto body and the engine case. but then that will throw the chains out of alignment
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I think Jim's comments were more directed to heat coming off the barrels, which might be 300 deg. F or more.

The timing chest is well bathed in oil, and therefore should not exceed the oil temperature, which is about 200 deg F max. (Except in short burst of power) Therefore, heat conduction from the timing chest should not be a factor.

As I noted in a previous post, a small air scoop, or one on each side of the barrell base, might mitigate the heat problem with the super magnet magnetos.


Slick
 
Joe Schlaberdowski said:
Do we have any old "replies" that show with pictures the necessary machining to the 850 cases to fit a mag behind the cylinders? Also, can you machine a right side Atlas case to fit an 850 commando engine in order to more easily mount a mag the old way? Or was so much changed it's 'apples to oranges'?
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I don't know of any, Joe. All the pictures I've found only show the parts required, and the complete engine with the mag already installed. I don't have the cases I had that were so modified, and didn't take any pictures when I had them back in the '70s and '80s. I used it for a 920 cc engine in my road racer, and it eventually developed cracks on both drive and timing sides, so I threw it out. These two pictures show at least some details of how Ron Wood fitted the Lucas mag to Commando cases using an Atlas timing cover. As Jim Schmidt pointed out, it does require some modification to the timing cover to match the Commando case.

Lets talk magnetos.
Lets talk magnetos.


Ken
 
texasSlick said:
I think Jim's comments were more directed to heat coming off the barrels, which might be 300 deg. F or more.

The timing chest is well bathed in oil, and therefore should not exceed the oil temperature, which is about 200 deg F max. (Except in short burst of power) Therefore, heat conduction from the timing chest should not be a factor.

As I noted in a previous post, a small air scoop, or one on each side of the barrell base, might mitigate the heat problem with the super magnet magnetos.


Slick
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yes he did but the heat path will be through the case of the magneto which is bolted to the timing chest... the oil temp , will go through the armature and bearings to the points... Certainly my Alton starter does not get especially hot and it is exposed to the same barrel temp, but then there is no heat conductive connection between it and the crankcases or timing cover... What Europeans like me tend to forget is just how hot it gets in parts of the states, maybe supermagnet magnetos would be ok in the UK. scoops would be simple and if they picked up cool air worth while, but what about when stuck in traffic
 
oldmikew said:
yes he did but the heat path will be through the case of the magneto which is bolted to the timing chest... the oil temp , will go through the armature and bearings to the points... Certainly my Alton starter does not get especially hot and it is exposed to the same barrel temp, but then there is no heat conductive connection between it and the crankcases or timing cover... What Europeans like me tend to forget is just how hot it gets in parts of the states, maybe supermagnet magnetos would be ok in the UK. scoops would be simple and if they picked up cool air worth while, but what about when stuck in traffic
Click to expand...

Heat ONLY travels from a place of high temperature to a place of LOWER temp. If the magneto were to approach 300 deg F due to hot air coming off the barrels, then it would be advantageous to have the LEAST thermal resistance between the magneto and timing chest, so heat could easily conduct from the hot (300F magneto body) to the relatively cool (200F) timing chest.

Stuck in traffic is a problem with air cooled engines. I submit, if one is not cognizant of the danger, losing the strength of the supermagnets may be the least one could lose.

If your Alton starter does not get overly hot, neither would a magneto.

Slick
 
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Slick,
Surely the barrel loses its heat to the throat of the crankcases and to air when in sufficient volume and flow. Air is not an especially good conductor of heat and I assume my Alton does not get overly hot for that reason as well as those I stated. Whilst our Commandos are oil and air cooled, i would have thought that the 200F oil temp you site would be for the bulk in tank temp, locally in the timing chest it may be hotter,and the actual metal itself may well be hotter still,depending on the rate of oil circulation..
But as regards Supermagneted magnetos , the magnets do not presumably fail every time the bike is started ,and so an incremental temp drop might make all the difference.
 
@oldmikew

We are now getting too far off the original topic of magnetos.

Heat Transfer 101 is adjourned. PM me for a private tutorial.

Slick
 
Well I will stick to mine hanging off the cam, no heat problems at all, easy to set up no machining at all and easy to maintain, I have no problems with it where it sits, in fact I like it there, works so well at slow speeds as well as high speed, idles great, starts first kick every time, no AAU to worry about, I don't care what others say about it, it works great for my set up, everyone has their own opinions and thats what this forum is all about, I had a good run out of my old Boyar set up and worked great as well on my Norton, I know how good JH maggies are having one on my Triumph that did 250,000 ks in 9 years of everyday riding and traveling all ove Asutralia in some of the hottest weather conditions around, the JH never let me down, nore did my second Boyar, but not everyone has had problem free troubles with what ever systems they run, ET ingitions and maggies do play up, nothing is perfect.
In 42 years of owning my Norton I have been blessed with a very reliable bike since new, keeping the maitenance up is all part of it and fixing things when they break, its all about what we love, MOTORCYCLES.
There are plenty other ignitions that work just as well, my choice is a Joe Hunt sticking out the side.

Ashley
 
When you fit the nice brand-new fairing to a race bike or do the lovely paint-job, you are certain to crash almost immediately. A Joe Hunt Magneto might be similar - what happens if it gets ripped off the timing case ?
 
acotrel said:
When you fit the nice brand-new fairing to a race bike or do the lovely paint-job, you are certain to crash almost immediately. A Joe Hunt Magneto might be similar - what happens if it gets ripped off the timing case ?
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I have set mine up with soft bolts if I do go down hard at high speed it will shear off but like I have said I have gone down twice now on the JH side and only damaged the front cover, cheap fix but remember if you do go down hard there will be more damage to your bike than the maggie, they are strongly built, you seem to be obsess with crashing all the time, in 42 years with my Norton on the road I have only been down a few times, I ride to stay up right, if you worry about crashing all the time you will, you just got to be aware what is going on around you.

Ashley
 
Ash, Alan is a racer and racing makes you superstitious.

A racers superstition makes the timing cover mounted mag look like 'tempting fate'.

Racers don't like to temp fate!

Underneath all the leather and bravado, racers are just like a bunch of old women really ...!
 
My first JH that I put on my Triumph came off a race bike my mate use to race, he had a lot of success with the racer with the JH out the side, he was the one that told me to use soft bolts to mount it, he crashed the Triumph on a high speed corner on the maggie side the bolts sheared off and the maggie slid away from the sliding bike, the maggie survived the crash, his bike was damaged badly and he walked away with a few battle scares on his body, the only damage to the JH was a few scraches on the housing, the bike never raced again thats why I ended up with the maggie, Don who crashed the bike was the mate that got me into Nortons all those years ago.

Ashley
 
The side mount mag spins opposite direction and has different points than the behind the cylinders mag - you can't mix them and they have different armatures. I've sold a lot of both types. If there's ever a problem - I hear about it and I help fix it. But no one who has actually owned and used a modern JH mag has EVER complained to me about the super magnets losing strength.
 
In racing, crashing is a fact of life. I know I have a real problem, because as soon as my motor fires up, I am never going to crash again. Away from racing, I know that is not the reality of the situation. If I really end up in the shit, I always pull the bike down so that it simply slides down the road on it's side or I get it onto the grass. These days I never have the big somersalt and tumble or freeze and hit the fence. You learn not to do that. With most corners on race tracks, they are set up so you can crash safely. If you go down while trying hard, it is usually OK. It is when stupidity prevails that it becomes dangerous. With beginners, ego and the adrenalin rush are a major danger.
 
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