Lets talk magnetos.

Bernhard · Nov 21, 2017

Lucas were notorious for producing cams for the K2F that were anything but 0 and 180 degrees, the stoning method was the hard way to correct them.

There was a whole advice page on how to use mag bearing shims cut into ¼ insert the correct corner to correct them, in the now closed, Old Classic Bikes Forum, perhaps you could ask kindly for them to fish it out for you from the archives?

https://www.accessnorton.com/NortonCommando/temporarily-closing-other-classic-bikes-forum.17057/

texasSlick · Nov 21, 2017

Bernhard said:
There was a whole advice page on how to use mag bearing shims cut into ¼ insert the correct corner to correct them, in the now closed, Old Classic Bikes Forum, perhaps you could ask kindly for them to fish it out for you from the archives?

https://www.accessnorton.com/NortonCommando/temporarily-closing-other-classic-bikes-forum.17057/

Shimming up a corner is a bodge! The correct way is to shift the cam ring diametrically within the housing, explained in detail here ....

https://www.accessnorton.com/NortonCommando/setting-up-and-timing-a-k2f-magneto.19685/

Regarding cost for a magneto rebuild ...... it runs about $US 450 - 500 and is not all labor! The price includes a rewind of the armature (about $100) and parts ranging from bearings to slip rings and high tension pickups, which we all know are not trivially cheap.

When I said the firing mismatch could be easily corrected, I was not referring to such a rebuild, which IMO, is NOT a DIY project. Only, the proper cam ring shimming to correct firing mismatch is simple.

PM me should anyone require help on this.

Slick

Triton Thrasher · Nov 21, 2017

Shimming a corner is a bodge but it’s up to the engineering standard of the rest of the K2F.

Joe Schlaberdowski · Nov 21, 2017

Is it the cam ring that's out of true, or the housing in which it sits? If it's the cam ring, wouldn't it be better to get a properly machined ring than to shim one that's not right to begin with? I sort of remember that, on the old Lucas, it's held in place by the screw on end cap that was kept from unscrewing by a tab at the top of the mag body that fitted into the longitudinal grooves around the outside of the cap. Don't remember what kept the ring from turning, but it must have been a small notch and key or something like that. I do remember that the ring (at least on mine) was rather free to come out and care had to be taken to make sure the end cap was on tight

texasSlick · Nov 21, 2017

Joe Schlaberdowski said:
Is it the cam ring that's out of true, or the housing in which it sits? If it's the cam ring, wouldn't it be better to get a properly machined ring than to shim one that's not right to begin with? I sort of remember that, on the old Lucas, it's held in place by the screw on end cap that was kept from unscrewing by a tab at the top of the mag body that fitted into the longitudinal grooves around the outside of the cap. Don't remember what kept the ring from turning, but it must have been a small notch and key or something like that. I do remember that the ring (at least on mine) was rather free to come out and care had to be taken to make sure the end cap was on tight

If the housing is out of center, that means the rotor is likely out of center, and centering the rotor is not a DIY project unless one is sufficiently skilled with proper facilities/tools. BTW, tipping a corner of the housing to tweek a timing mis-match, is a sure way to create a non-centered rotor.

Assuming the housing and rotor is properly centered, the likely culprit that causes mis-matched firing is a poorly machined cam ring which was commonplace in the late 50's and 60's. Machine tools, worn out by the demands of WWII, is given as the cause for these cam rings. You are correct that replacing such a poorly machined cam ring with a new CNC ring is the preferred fix.

Lastly, even with a new, properly machined cam ring, there can be some firing mis-match that is corrected by shimming the cam ring to exact center.

A quick check for firing mis-match is to check the point gap on both ramps of the cam. If the gaps are not equal to within 0.001", there is likely firing mis-match present. Of coarse, only a degree wheel will tell for sure, and by how much.

Slick

Triton Thrasher · Nov 21, 2017

BTW, tipping a corner of the housing to tweek a timing mis-match, is a sure way to create a non-centered rotor.

No it’s not. The shimming is often as thin as a couple of thicknesses of Al foil. I know: I’ve done it and done the miles afterwards.

Grinding the cam is certainly better engineering, but it’s a lot of work.

acotrel · Nov 21, 2017

If you were prepared to jet twin carbs separately, the error in ignition timings between each cylinder might not be so important ?

texasSlick · Nov 21, 2017

acotrel said:
If you were prepared to jet twin carbs separately, the error in ignition timings between each cylinder might not be so important ?

Is 25 degrees important? I once helped out a chap from Oz who had that much. Others on this Forum have reported similar degrees of timing mis-match.

Alan, perhaps if one got the timing spot on, it would not be necessary to jet twin carbs separately!

Slick

Triton Thrasher · Nov 21, 2017

7 crankshaft degrees discrepancy was enough to make my T110 act funny.

I have found that getting it even is the owner's job, whichever way you do it. Magneto professionals don't appear to take the matter seriously.

texasSlick · Nov 21, 2017

Triton Thrasher said:
7 crankshaft degrees discrepancy was enough to make my T110 act funny.

I have found that getting it even is the owner's job, whichever way you do it. Magneto professionals don't appear to take the matter seriously.

I fully agree with you on this of your recent posts on magnetos. I leave it to the readers to sort out where we disagree.

My K2FC came back from a magneto rebuilder with 6 degrees mismatch. I found the cam ring to be worn on one ramp. The rebuilder stated he was reluctant to put in a new cam ring because it would add $US100 to the cost, and customers were already in shock over the customary price. Lesson to be learned ..... evaluate the cam ring before shipping the mag off to a rebuilder, or instruct him to evaluate and replace if in his judgement it is best to do so. From my experience, and from that of others whom I have helped with their K2F's, mag rebuilders, as you say, "do not appear to take the matter seriously".

Yes, 6 or 7 degrees can make an engine run "wonky". After getting my Atlas spot on, the vibration seems less, and the idle is so steady at 1000 rpm, the tach needle seems to be painted on.

Slick

Danno · Nov 21, 2017

texasSlick said:
I fully agree with you on this of your recent posts on magnetos. I leave it to the readers to sort out where we disagree.

My K2FC came back from a magneto rebuilder with 6 degrees mismatch. I found the cam ring to be worn on one ramp. The rebuilder stated he was reluctant to put in a new cam ring because it would add $US100 to the cost, and customers were already in shock over the customary price. Lesson to be learned ..... evaluate the cam ring before shipping the mag off to a rebuilder, or instruct him to evaluate and replace if in his judgement it is best to do so. From my experience, and from that of others whom I have helped with their K2F's, mag rebuilders, as you say, "do not appear to take the matter seriously".

Yes, 6 or 7 degrees can make an engine run "wonky". After getting my Atlas spot on, the vibration seems less, and the idle is so steady at 1000 rpm, the tach needle seems to be painted on.

Slick

That was close to my experience. Then the Boyer hit the market and I haven't looked back. Hot spark and precise timing for a fraction of what it cost to rebuild the K2F. Gotta have a battery for the lights anyway.

ashman · Nov 21, 2017

I have run years without a battery for my lights with my maggie, battery eliminator straight off the ALT not the best of light but it works fine for me.

Ashley

texasSlick · Nov 21, 2017

ashman said:
I have run years without a battery for my lights with my maggie, battery eliminator straight off the ALT not the best of light but it works fine for me.

Ashley

I use a mini 2.5 AH battery only to keep the lights up at idle. Such a battery also assists the electronic rectifier/voltage regulator to work more efficiently (the battery functions like a capacitor).

The electronic ignitions may top a magneto on the dyno, but the magneto ignition is the least likely to leave you on the road (providing the internal capacitor in the K2F has been refreshed).

Slick

acotrel · Nov 21, 2017

I've had K2Fs fully reconditioned and they have still failed at the first provocation. If you are racing, they become a very expensive exercise when you have to go home and lose your entry fee. Rotating magnet is the only way to go - usually the condenser is outside where you can get to it. I think when the condenser fails in a K2F, it shorts. So you cannot even hang another condenser on the earthing terminal, to get by.

Triton Thrasher · Nov 21, 2017

texasSlick said:
I fully agree with you on this of your recent posts on magnetos. I leave it to the readers to sort out where we disagree.

Slick

I've done dremeling of the ramp and shimming under the cam ring too, at different times. I don't know what I'd do with a 25 degree difference!

Triton Thrasher · Nov 22, 2017

acotrel said:
I've had K2Fs fully reconditioned and they have still failed at the first provocation. If you are racing, they become a very expensive exercise when you have to go home and lose your entry fee. Rotating magnet is the only way to go - usually the condenser is outside where you can get to it. I think when the condenser fails in a K2F, it shorts. So you cannot even hang another condenser on the earthing terminal, to get by.

Never raced, but if you tell me a K2F can’t stand the sustained high revs involved, I’m not all that surprised.

On the road, old Brit big twins aren’t kept at much over 5000 rpm for all that long. I do have trouble with magnetos, but not usually roadside failures trouble.

acotrel · Nov 22, 2017

Perhaps what is NOT being said is sometimes more important than what IS being said ? I wonder how many people have ever fitted a magneto to a Commando which was NOT a Joe Hunt. Jim Schmidt claims that his magneto lost magnetism due to heat, but the only bike I've seen Jim use in his videos has had a featherbed frame. So it is probably either an Atlas or a 650SS. For me using a Joe Hunt is not an option. It is too vulnerable if a serious crash happens. Fitting a Lucas K2F or SR type means machining the crankcases and using an Atlas or 650SS idler gear with the sprocket. Machining to fit a gear means setting up to get the meshing right and if a chain is used, that means another chain tensioner. So in effect talking about magnetos for a Commando is a 'pointless exercise'. Batteries are the bane of my life and the lithium ones seem very expensive for what they are. I currently got a new battery sitting on the shelf in my shed. If I put the acid into it, it means I have to trickle charge it to maintain it, or it will die like all the others. A magneto would be good, but I think I cannot go there.

ashman · Nov 22, 2017

Joe Hunt make 2 maggies for the Nortons one behind the motor for the older models and the one that runs straight off the cam, the old Lucas maggies are so out of date, but I will be running a Lucas competition maggie on my 650 Domie as it came with the pile of parts a Domie in boxes, it was a ex Mike Ferral race bike, the Joe Hunts are easy to work on four screws to take the cover off and points, condenser and coil are there and I think Jim Schmidt only had troubles with a condenser if you read back, I run Jims PWK flatslide carbies with my Joe Hunt they work so well together, but thinking about saving up and getting his newer carbies that he now sells.

Ashley

lcrken · Nov 22, 2017

acotrel said:
Perhaps what is NOT being said is sometimes more important than what IS being said ? I wonder how many people have ever fitted a magneto to a Commando which was NOT a Joe Hunt.

Well sure, I've fitted a total of 3 ARD mags to Commandos, one the old Fairbanks Morse style, fitted behind the timing side like an Atlas, and two of the later, more compact ones that drive off the end of the camshaft. And yes, I did also, at least for a while, have a Joe Hunt fitted to the timing side like the ones Jim sells.

Also, as I pointed out earlier, Ron Wood modified his Commando cases to fit Lucas racing mags in the Atlas position.

Back in the '70s, HPI ( a Norton shop in Southern California) modified a number of Commandos to take the old style ARD mag behind the timing side.

Several other Norton folks, including Jim Comstock, have done the modification to the Commando cases to take either the Lucas or one of the Fairbanks Morse style (Joe Hunt, old ARD) mags in the Atlas positon.

So in effect talking about magnetos for a Commando is a 'pointless exercise'.

Hard to call it a pointless exercise when so many people have already done it.

Having said that, I run electronic ignitions (Trispark) on my street Commandos, and only have a magneto on the race bike that I'm running in landspeed events. I like the idea of a hotter spark to fire the nitrous mix at high rpm, plus that's what I used when I used to road race the same bike, but I suspect a good EI would work just as well.

Ken

Joe Schlaberdowski · Nov 23, 2017

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'?