650 Norton Vibration and Balance Factor

Rohan · Feb 14, 2013

So now we have 2 different fixes - for the same problem ??

If you take the mag ring off and play with them, they seem to vary a bit...

KenF · Feb 15, 2013

I'd be very worried about putting quarter shim(s) under corner(s) of the end housing. It will increase the end float of the armature. That will increase the radial play of the CB end of the armature. That will make the firing points unpredictable. Even if quarter shim(s) are taken out from under the opposite corner(s) of the end housing, the poor old bearing won't be running true. And I can't see how any of this can cure the problem, unless it's some second-order effect.

The reason for uneven firing intervals in a K2F is if the cam ring is not symmetrical about the axis of rotation of the armature. That can be caused by:-

the cam ring not itself being symmetrical, but in my experience that is rare, even with a worn cam ring, unless somebody has stoned it
the cam ring being loose
the end housing being incorrectly machined, but in my experience that is rare
the armature axis not being fixed, either because the end float is incorrect so that there's radial play between the inner race and the outer race, or because the insulator is shot so that the outer race can move in the end housing
the armature axis being off-centre from the cam axis, because the bearing insulator isn't holding the outer race central in its recess.

In my experience, the last reason is usually the one (unless the cam ring is loose).

Ken
http://www.brightsparkmagnetos.com

Bernhard · Feb 15, 2013

KenF said:
I'd be very worried about putting quarter shim(s) under corner(s) of the end housing. It will increase the end float of the armature. That will increase the radial play of the CB end of the armature. Even if quarter shim(s) are taken out from under the opposite corner(s) of the end housing, the poor old bearing won't be running true. And I can't see how any of this can cure the problem, unless it's some second-order effect.

The reason for uneven firing intervals in a K2F is if the cam ring is not symmetrical about the axis of rotation of the armature. That can be caused by:-

the cam ring not itself being symmetrical, but in my experience that is rare, even with a worn cam ring, unless somebody has stoned it

the cam ring being loose

the end housing being incorrectly machined, but in my experience that is rare

the armature axis not being fixed, either because the end float is incorrect so that there's radial play between the inner race and the outer race, or because the insulator is shot so that the outer race can move in the end housing

the armature axis being off-centre from the cam axis, because the bearing insulator isn't holding the outer race central in its recess.

In my experience, the last reason is usually the one (unless the cam ring is loose).Ken quote]

Yes, yes and yes. They were my concerns too, until I came to the conclusion that the magneto bearings were by far cheaper to replace than chewed up pistons. It was the lesser of the 2 evils as far as I was concerned.
Re; “That will make the firing points unpredictable.” - Maybe true to a small extent, but if you read below and have followed my own experience with these bikes the bike did not eat pistons before I messed up the magneto, and after eating no less than 6 pistons after the “expert” fix-How come the bike did not eat pistons before I screwed it all up :?:
Ignition timing is critical, if the engine requires 27 degrees on full advance then 27 degrees it is, there is no leeway. The green Norton workshop manual instruction of splitting the difference of a magneto timing of say, 6 degrees difference between the two cylinders, so I cyl is 3 deg too far advanced and the other 3 deg too far retarded is a joke .
Me thinks that there are hundreds if not thousands of old British iron running out there with either a faulty K2F magneto ( with consideration of the way this company send out parts, that could have been better machined in the first place) or has one that has been corrected at some point in it’s life.

I remembered in my naïve youth how I had removed and stripped that magneto to replace a leaking oil seal and two oily/dirty quarter pieces of metal fell out- I did not know what these was for, or where they came from and consequently failed to replace them – hence my piston troubles on the Atlas. You live and learn.

Bernhard · Feb 15, 2013

Rohan said:
So now we have 2 different fixes - for the same problem ??

If you take the mag ring off and play with them, they seem to vary a bit...[/quote

No kidding –how do I know :?: .............as I have reported before, I purchased a brand new boxed Lucas K2F Camring in the 1970s took it to work and clocked it up on a Milling machine dividing head and ran a .001 thou Verdict clock gauge to see if the two lobes were 0-180 degrees apart- they were not- they were four and a half degrees out.

acotrel · Feb 15, 2013

My friend was delighted when I gave him a beautiful Lucas racing K2F magneto. On my short stroke triumph I always used a Lucas SR4 magneto with the diagonally opposite leads paired to the plugs. My friend with the very fast 650 Triumph used, and still uses an SR2. They a re the same thing - the magnet rotates, and the coil and capacitor are not part of the armature. Manx Nortons and G50s used the same configuration SR1R which is a racing magneto whereas the SR2 and SR4 are both industrial models. I believe the racing SR has a stronger armature, but I've never known the industrial type to fail. My 500cc Triumph used to rev reliably to 10,500 rpm, and it never developed a miss in 12 years of racing. I bought the SR4 brand new in about 1968 for $30 when a racing magneto cost five times that amount and most gave trouble as soon as the motor got hot.

The Lucas SR1R (SR2 bits fit ) requires a platform and adaptor plate to fit to a twin.:

http://s261735181.e-shop.info/shop/arti ... 2520004%26

Bernhard · Feb 16, 2013

acotrel said:
My friend was delighted when I gave him a beautiful Lucas racing K2F magneto. On my short stroke triumph I always used a Lucas SR4 magneto with the diagonally opposite leads paired to the plugs. My friend with the very fast 650 Triumph used, and still uses an SR2. They a re the same thing - the magnet rotates, and the coil and capacitor are not part of the armature. Manx Nortons and G50s used the same configuration SR1R which is a racing magneto whereas the SR2 and SR4 are both industrial models. I believe the racing SR has a stronger armature, but I've never known the industrial type to fail. My 500cc Triumph used to rev reliably to 10,500 rpm, and it never developed a miss in 12 years of racing. I bought the SR4 brand new in about 1968 for $30 when a racing magneto cost five times that amount and most gave trouble as soon as the motor got hot.

The Lucas SR1R (SR2 bits fit ) requires a platform and adaptor plate to fit to a twin.:

http://s261735181.e-shop.info/shop/arti ... 2520004%26

Can you tell us if there is enough room under the carbs to fit one of these Lucas SR4 magneto’s under the carbs on a f/bed Norton engine :?:

acotrel · Feb 17, 2013

Mine was fitted to a Triumph 650 motor which had 12mm removed from the top of the barrels, the carbs on a Norton are usually angled upwards. There should be plenty of r oom. However you will find it is essential to build a stable platform under the mag, and make a decent triangular plate to secure it to the crankcase face. The SR looks heavy, but it weighs much the same as a K2F. I've had even those come loose and break studs and the corner off the magneto through racing. The only thing you might not like is that it will definitely look non-standard, but it is a really good answer for something which is a real pain in the bum. Lucas K2F magnetos are better than the old BTH magnetos used in the fifties. That's like saying Ford Anglias are better than Standard Vanguards, when you know you can buy a Porsche that makes them both look stupid..

acotrel · Feb 17, 2013

If you go to a dealer in old industrial engines or marine engines you should be able t o find an old SR. You can still buy all the parts to convert them from single to twin or four cylinder work. There are a few on Ebay - cheap as chips. If you try and fail you probably won't lose $100. There is one thing you should do if you use one of these , fit longer screws to hold the coil in place, and drill and lock wire them. If the coil comes loose, the bike will probably start misfiring. However on a road bike, that should never happen, you don't get the same level of vibration. The SR is a much better option than a rotating coil magneto. You need to source the twin cylinder end cap, cam and points to covert the SR1 to an SR2. This is much better than being at the mercy of idiots who pretend to recondition magnetos. Playing with rotating coil magnetos can cost you an absolute bomb.

http://www.ebay.co.uk/sch/i.html?_nkw=lucas+sr+magneto

acotrel · Feb 17, 2013

My brother, our friends, and I have a long frustrating history in relation t o magnetos. In the early days there was an auto electrician in Melbourne who used to rebuild them unsucessfully. These days the 'expert' is at Chiltern, near me in NE Victoria. - Equally unimpressive. We have just re buiolt an 880JAP sidecar which has 2 BTH magnetos. We have tried to race it twice, the latest effort is a complete rebuild/recondition of the magnetos for the second time. We cannot use the SR type because the bike is historic, so we again go down the painful path.

http://www.youtube.com/watch?v=Rk_Nkv0imrw

http://www.youtube.com/watch?v=wOcznU_dKt0

Rohan · Feb 17, 2013

There must be tens of thousands of rebuilt K2F's in use happily running around all around the world (hundreds of thousands ?).
Find someone who comes recommended, and have it done properly.
With modern wire, insulator material and capacitors, should last a lifetime.

My magneto rebuilder gave me the guided tour of his works - winding lathe, epoxy potting material to make it waterproof and test rig to try it under heat. Very rare he gets to see them again - he was in the Velo club, so they'd notice if one cylinder goes off.....

acotrel · Mar 1, 2013

Velocette owners are used to bikes that don't want to start, their bikes are designed that way, and a K2F magneto is a necessary addition. There must be thousands of owners of old Triumph racing bikes around the world who've loaded up all their tools and bikes after paying exorbitant entry fees , and turned up to meetings only to have the bike start missing due to crappy K2F magnetos.

Rohan · Mar 1, 2013

acotrel said:
and turned up to meetings only to have the bike start missing due to crappy K2F magnetos.

Are you blaming the magneto, or the owners ?!!

acotrel said:
Velocette owners are used to bikes that don't want to start, their bikes are designed that way, and a K2F magneto is a necessary addition.

Velo's don't use a K2F.....
The low kickstarter gearing ratio is respomsible for most of that problem.

Someone here has solved that by fitting electronic ignition into the maggie housing - big sparks at very low engine kicking speeds.
But then your generator/battery/wiring ALWAYS has to be in tiptop shape.

Bernhard · Mar 2, 2013

acotrel said:
Velocette owners are used to bikes that don't want to start, their bikes are designed that way, and a K2F magneto is a necessary addition. There must be thousands of owners of old Triumph racing bikes around the world who've loaded up all their tools and bikes after paying exorbitant entry fees , and turned up to meetings only to have the bike start missing due to crappy K2F magnetos.

You sound like you had a bad experience regarding Lucas magnetos.
As a former Velo owner Rohan is right about the low geared kick start, hence they have to go through a drill to kick the Velo single into life.
Whether you have a K1F or a K2F I constantly had to change the magneto oil seal as the winding became engulfed in oil.

The K2Fs were slightly better when they were competition magnetos. (K2F competition)

Triton Thrasher · Mar 2, 2013

Bernhard said:
acotrel said:

Whether you have a K1F or a K2F I constantly had to change the magneto oil seal as the winding became engulfed in oil.

The K2Fs were slightly better when they were competition magnetos.

Click to expand...

All the little weaknesses in bikes interact to exponentially increase breakdown frequency. The weakness in crankcase breathing and the oil drain-down find the weakness in magneto sealing.

acotrel · Mar 2, 2013

How many instances do you want me to recite where guys have gone to race mee tings only t o have the motor start missing as soon as it got hot due to rotating coil magnetos ? The latest one was last year when a friend built a beautiful 650 Triumph speedway outfit. Had he magneto done by the expert - same old- same old. Then we did two lucas magnetos for the 880 JAP - same old- same old. With the JAP the appearance has to be right , so we are pretty much stuck with the rotating coil garbage. I think those magnetos on my brother's JAP are now filled with modern day electronics , but we've been through the same old bullshit yet again. It missed like buggary at the last meeting at Wangaratta in November 2012. I used a Lucas SR rotating magnet magneto on my short stroke Triumph - revved regularly to 10,000 rpm for about four meetings per year for 12 years that I had it , and it has been on the bike and raced by others for t he last twenty years . It has never missed, and never failed.
Rohan, you might be able to tolerate magneto breakdown on your road bike, and get it home on a trailer. Our bikes are already on the trailer and taken at least 200KM, and sometimes 700KM. We go with the intent to win races, not waste money tolerating antique magnetos which fail every five minutes. There is a simple answer to all bike problems - if it gives you the shits, re-engineer it, and do the job properly

Rohan · Mar 2, 2013

I'd expect any magneto which has been rebuilt PROPERLY, with modern materials, to outlast my lifetime.
I'm not aware of any magneto failures in my roadbikes - not since the magnetoes were rebuilt, anyway.
(not that some of them have had much/ any use ! - or the bike they go into finished yet !)
Kick kick kick - unrebuilt maggies may be a different matter - kick kick kick

P.S. Why don't you name who is doing these sub-standard rebuilds ?
PPS. Someone did mention compy magnetos - are you using roadbike components ? on a race engine ??
Lucas did produce racing maggies for a reason. They have to stand the heat, for one...

Triton Thrasher · Mar 3, 2013

Sometimes I am baffled by Acotrel.

Is he giving his magnetos to crooks or incompetents to repair, then ranting on here about K2F design?

It is not be the most precise or robust ignition system in the World, but it does work: the engine starts and runs. I know because I use them. This stuff about "5 minutes between breakdowns" is just silly. What part broke and why?

When misleading advice is posted, the arguments continue. No doubt we'll see some more "last word-ism" here, in long posts.

johnm · Mar 3, 2013

Acotrel is commenting as an Ozzie living at the second to last place in the British bike supply chain. I spent 30 years at the bitter end of the chain - NZ.

And there was a time I would have cheerfully burned down the Lucas factory - not really but it was close

Lucas rotating coil mags are total rubbish- all of them. And the racing mags are not much better - read what Rod Coleman has to say in his book "The Colemans" . He beleives he lost the 500 World Championship on his AJS Porcipine twin due to Lucas mag failures. I have a friend who lost a NZ championship in the 1960s due to a brand new Lucas racing mag failing on his Manx 500 m short of the finish. He threw the mag into Wellington harbour and never used a magneto ever again.

Maybe in the UK their mags were fine but I can tell you by the time they got to us they were total s***.

My bike uses a Morris mag rotating magnet mag. It has worked perfectly for 8 years.

(But yes - Velos do not use K2F mags. Original equipment was BTH. My friends Venom does use a twin Morris mag - but then it is also twin plugged)

Triton Thrasher · Mar 3, 2013

Were I racing, I would most likely use a total loss battery system. And in this day and age, I would most likely use an electronic ignition.

But on a roadgoing pre-unit, I have found that a good magneto is the most dependable and convenient of several ignition systems that I have used. Better mags than the K2F could be made, but availability and familiarity count in its favour.

acotrel · Mar 3, 2013

Years ago I dropped my Triumph Thunderbird on a slippery road, and the BTH magneto simply stopped working - took the bike home in a trailer. With the Lucas SR type of magneto, you can take the end off while it is on the bike and replace the coil, and the capacitor is outside and easily replaced. You don't usually have problems due to armature windings and internal capacitors failing. The rotating magnet type is common on all good old British racing singles, and the SR2 industrial magneto is eons ahead of a K2F. The guys who repair them in Australia are not crooks, but if you get a rotating coil magneto repaired here , you have to be lucky to have it keep going without breakdown. It is usually the main difference between a slow racing Triumph and a fast one. I use total loss system on my Seeley - a Boyer with a double ended Honda coil. It has never failed, but the bike developed a miss when I had battery problems. The motor only revs to 7,000 rpm, and it is low compression, so the ignition system doesn't have to do much.

650 Norton Vibration and Balance Factor

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