Magneto timing

texasSlick said:
EasyCaps seem to work fine. However, to use an EasyCap, the internal (shorted if in failure), capacitor MUST be disconnected. This requires removing the cam housing, which will likely upset the centering of the armature spindle. Few of us have the expertise and instruments to properly center the armature spindle.

Therefore, like John reply #32, I recommend a competant magneto rebuilder.

Slick
Click to expand...
FWIW I have had some luck centering the armature spindle with the magneto on the bench. This "technique" assumes the cam itself is machined accurately. With a degree wheel on the magneto drive shaft - washers and a nut on a degree wheel with a small center hole - you can loosen the three cam housing fasteners. If you push the cam housing in different directions you can find the position where the points break at the same # of degrees on the degree wheel. Tighten the fasteners and verify. You can either use Texas Slick's technique for finding when the points break or a magneto timing light. (AO Services in the UK sells a simple magneto timing light).
 
Bodger said:
FWIW I have had some luck centering the armature spindle with the magneto on the bench. This "technique" assumes the cam itself is machined accurately. With a degree wheel on the magneto drive shaft - washers and a nut on a degree wheel with a small center hole - you can loosen the three cam housing fasteners. If you push the cam housing in different directions you can find the position where the points break at the same # of degrees on the degree wheel. Tighten the fasteners and verify. You can either use Texas Slick's technique for finding when the points break or a magneto timing light. (AO Services in the UK sells a simple magneto timing light).
Click to expand...

Newly made cam rings are very likely accurately machined, and this technique should get the spindle reasonably on center. However, this centering is ONLY in the plane that intersects the cam ramps. The spindle could still be off center in a plane 90 degrees perpendicular.

I think only a dial indicator, set up in a 90 degree offset, can properly center the spindle.

For the DIY'er, who insists on installing an EasyCap, or who otherwise feels he can go inside a K2F without wrecking something, your technique beats a blissful reassembly without regard to centering.

Slick

EDIT: This technique also must assume the cam housing is accurately machined.
IMO, not a good assumption if the housing is original manufacture. Cam rings made in the 60's were noted to be way off due to machinery being WWII worn out. Why not cam housings?
 
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texasSlick said:
The only problem I ever had with a Lucas K2F was after 40 years the internal capacitor crapped out. It was always a one kick starter.

It was rebuilt by Doug Wood, and I timed it dead nuts on both cylinders, which I subjectively feel has taken some of the vibration out of the engine. It is still a one kick starter, but my leg is not.

The new polystyrene capacitors will likely last 100 years.

Slick
Click to expand...

I wish I had your experience. But I went through 3 or 4 Lucas mags including the one that came with the bike. A couple were sent off to be rebuilt by "pros". They were rewound with new capacitors and I still had problems with them. Starting usually involved pushing the bike down the street. No doubt there are some Lucas mags that work very well but I've never been able to find one. The Joe Hunt mag went in 2009. I replaced the original single lipped oil seal with a double lipped seal and installed it the correct way (they come new with the single lip oil seal installed backwards). The oil seal spring should be facing the oily timing chest side (its oil tight now). I had to replace one condenser (easy to do on the Hunt). It generally starts 1st kick, runs clean and never misses (after keeping oil out of the mag & points).

The dual lipped seal I used is 15x35x7 #00607683

I went overboard and installed an aluminum collar with a 2nd smaller seal for the tapered part of the shaft to make sure a drop of oil never gets in there but I don't think its necessary. The 2nd seal is 14x24x6 #02583450

You also have to put sealer between the plate and the magneto or it will leak (they come new without sealer).

Magneto timing


The front points cover mount Magnetos (as on later Commandos) don't have an oil problem because there are two seals already in front of the mag.
 
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Johnnymac said:
Hi guys. I'm still trying to get my Atlas on the road. I finally got the K2FC magneto on the bike last weekend and my friend helped me time it. We set it to 32 degrees full advanced BTDC and it started up on the very first kick. I was very excited.

It runs like shit though. Idles nicely. but when giving it a bit of throttle, it pops and seems all over the place.

So question is, was 32 degrees BTDC full advanced the best way to set the timing? Thanks!
Click to expand...

Hi All.
Never setted my K2FC magneto on my Matchless G15 MK2.
Could you explain the way?.
Thank you.
Piero
 
texasSlick said:
Newly made cam rings are very likely accurately machined, and this technique should get the spindle reasonably on center. However, this centering is ONLY in the plane that intersects the cam ramps. The spindle could still be off center in a plane 90 degrees perpendicular.

I think only a dial indicator, set up in a 90 degree offset, can properly center the spindle.

For the DIY'er, who insists on installing an EasyCap, or who otherwise feels he can go inside a K2F without wrecking something, your technique beats a blissful reassembly without regard to centering.

Slick

EDIT: This technique also must assume the cam housing is accurately machined.
IMO, not a good assumption if the housing is original manufacture. Cam rings made in the 60's were noted to be way off due to machinery being WWII worn out. Why not cam housings?
Click to expand...
I agree that a dial indicator would be the gold standard, but not certain what you mean by 90 degrees to perpendicular in this context. Please explain.
 
Bodger said:
I agree that a dial indicator would be the gold standard, but not certain what you mean by 90 degrees to perpendicular in this context. Please explain.
Click to expand...

Bodger

Let me make two points:

1) I am not belittling your method ..... just saying it is better than naught, but may not be good enough.

2) I have never centered the spindle on a K2F, so am no expert. That said, it does not mean I cannot think thru the problem.

As I see it, the problem is exactly like centering a dowel rod in a 4 jaw chuck, the kind with independently adjustable jaws. One has to center the part in one plane first .... say the jaws at 3 and 9 o'clock, then rotate the chuck 90 degrees and center between the jaws that were at 12 and 6 o'clock. Then do again to check.

I am befuddled how the "pros" center the magneto spindle. Most likely they screw a bushing into one of the high tension ports, and use it to hold a dial indicator. This centers in one plane only. Just as in a 4 jaw chuck, one must check in a plane 90 degrees perpendicular. Perhaps, some rebuilders do it in one plane and call it good enough. I do not know if one plane centering is the standard,, but I do know several persons, who found, after having a K2F returned fresh from a rebuilder, that the spindles were, in fact, off center (robs ss as reported in another thread, comes to mind first.).

We need DynoDave to chime in on how it is done.

Hope this helps.

Slick
 
texasSlick said:
Bodger

Let me make two points:

1) I am not belittling your method ..... just saying it is better than naught, but may not be good enough.

2) I have never centered the spindle on a K2F, so am no expert. That said, it does not mean I cannot think thru the problem.

As I see it, the problem is exactly like centering a dowel rod in a 4 jaw chuck, the kind with independently adjustable jaws. One has to center the part in one plane first .... say the jaws at 3 and 9 o'clock, then rotate the chuck 90 degrees and center between the jaws that were at 12 and 6 o'clock. Then do again to check.

I am befuddled how the "pros" center the magneto spindle. Most likely they screw a bushing into one of the high tension ports, and use it to hold a dial indicator. This centers in one plane only. Just as in a 4 jaw chuck, one must check in a plane 90 degrees perpendicular. Perhaps, some rebuilders do it in one plane and call it good enough. I do not know if one plane centering is the standard,, but I do know several persons, who found, after having a K2F returned fresh from a rebuilder, that the spindles were, in fact, off center (robs ss as reported in another thread, comes to mind first.).

We need DynoDave to chime in on how it is done.

Hope this helps.

Slick
Click to expand...
Did not at all think you were belittling, just wanted to learn what you meant. Admittedly my "system" is crude, especially since it uses the cam ring as a datum point. But it seems to me that if a degree wheel shows the points opening repeatedly at the same degree on the wheel the spindle must be reasonably in alignment. Also curious to hear what Mr. DynoDave has to say.
 
Mr. DynoDave
that's
little d
dynodave
I will be going back to bed now but will by the end of this holiday weekend I'll try to have an initial description of procedure and might be able to come up with a few pix.
 
i read with some amusement About magnetos the lucas k2f like any magneto when new was ok but give it a few years and the windings do rot the secondary winding is soft soldered and nine times out of 10 there is a bad connection here all,green and festering
the only cure is a rewind , and a modern condensor
the armature should be checked for run out after assembling the drive shaft can be bent due to hamfisted mechanics
its easy to tweak the cam ring to give equal timing by carefull sanding with an emery drum sander on the lobes
ive made my own 50degree v twin rings succefuly out of single cyl ones
bth mags are far superior in construction and i would recommend them for racing
also the lucas sr ,fairbanks ,dixie,hunt clones are inherently more reliable as the winding isnt flying round at 4000rpm and you can just slacken 2 srews and change ths coil without dismantling timing cover etc

timing disc on a 1950s bike ?
every bike had a measurement btdc
and you get the bike on compression stroke bring it up to tdc, now put a pencil in the plughole and make a mark on it by pushing and rotating against the thread
remove the pencil and mark the distance btdc most old bikes around 3/8,below the top mark mag should be on full advance by lever on bars or by locking the atd unit fully in direction of rotation
i use wooden clothes peg legs as wedges
now look inside the mag and make sure the brass section on the slip ring corresponds with the cyl youve got the pencil in put a rizla paper between the points anx rotate the armature by fingers on drive taper or points end till paper is possible to slide out just
fit drive pinion,manual put a socket against it an one light tap with a hammer should lock it on the taper fit nut and nip up
with the atd unit fit the wedged open unit on the spindle and nip up the nut finger tight making sure the shaft is not rotating
it helps to run a tap and die over the threads so theres no resistance due to bashed theads etc and no nyloc nuts please thread is 3/8 bsf
when this is done turn the motor backwards and bring it forward so you can just slide that fag paper out then check your btdc distance with the magic pencil
if your happy with your timin you can now make a piston stop out an old plug that will make it easy for the future just turn engine till piston hits the stop at the pre determined measurement

oh tto turn the engine remove plugs put in gear and move wheel ,rear one not front

why do i know this ? i have been rewinding my own magnetos for years
i have a,german Aumann, winding machine and a very large ancient dc magnetising machine and a home made vacuum impregnating set up
i have a few hundred modern condensors too
when i finally hang up my welding mask i will do it as a service to you all
its a time consuming buisness it takes me around 2 days to strip ,rewind, vacuum varnish ,pot in a new capacaitor and run on a test rig for 12 hrs slow rpm and high rpm at 5mm gap then 8 mm suicide gap
i use military grade wire and mica paper and kapton as an interleaf material
the winding is progressivly wound in a taper fashion getting narrower near the top as the voltage gains with every layer so it naturaly wants to jump to earth
so ever measure must be taken to stop this
its not unknown to fully wind one and maybe when your finished it put an ohmeter thru it to dicover youve broken it
so eat shit and start again the wire is under 3 thou the real competition mags use even finer stuff more turns ya see
bigger spark
hope this helps understand the black art
ps an old guy up here sent a lucas 1920s
single mag away to an english specialist and was charged £700 not even an itemised invoice
Dick Turpin still at large isnt he
 
The analysis of the centering of the magneto main shaft in relation to the center of the cam ring is the basic process path. The next goal will includes the cam profiles to be mapped on the cam ring and verified to spec-mainly 180 degree magneto @ points opening representing ignition spark period exactally 360 degree crankshaft.
Measurements and dimensions.
The points end bearing housing has a bearing that rides in it, a magneto armature shaft. The Center Of Rotation of THIS shaft is what is action center of this magneto's universe. The shaft COR needs to run perfectly centered in the cam ring pocket bore. Complication is that the cam ring bore is a seperate machined surface from the bearing pocket bore and they may necessarily have been machined concentric, The shaft bearing insulator shim is the only means to move the COR for alignment purposes.

The bearing can not withstand the arcing spark electrical current running from the race, to the balls, to other race.... That is the reason for the carbon contact/brush on the grounding slip ring and the insulators to electrically isolate the bearings from being the spark conductor..

The insulator shim materials are available to use today's kevlar papers in various thickness' to move the bearings physical position. The movement can easily be changed by amount and angle as needed. The final bearing insulator thickness' is around .070" two half shims must total the final .070 needed. instead of .035 + .035, you could use .030 and .040 to move the COR by .010" in any angle based upon angle of shim placement.

Procedure for measuring.
In the points end of the armature there is a taper which a custom fixture for mounting a dial indicator. can be mounted. alternate is an old points
plate suitably modified for attaching a machinist "last word" gauge or similar.

To check if the added point openings are 180degrees will require a full mag assembly with a degree wheel attached.to the shaft and a buzz box or sensitive ohm meter.

More can be said and in finer detail, but the basic goal and details are spelled out .
You also need a drawer full of kevlar paper size assortment and good scissor skills.
 
dynodave said:
The analysis of the centering of the magneto main shaft in relation to the center of the cam ring is the basic process path. The next goal will includes the cam profiles to be mapped on the cam ring and verified to spec-mainly 180 degree magneto @ points opening representing ignition spark period exactally 360 degree crankshaft.
Measurements and dimensions.
The points end bearing housing has a bearing that rides in it, a magneto armature shaft. The Center Of Rotation of THIS shaft is what is action center of this magneto's universe. The shaft COR needs to run perfectly centered in the cam ring pocket bore. Complication is that the cam ring bore is a seperate machined surface from the bearing pocket bore and they may necessarily have been machined concentric, The shaft bearing insulator shim is the only means to move the COR for alignment purposes.

The bearing can not withstand the arcing spark electrical current running from the race, to the balls, to other race.... That is the reason for the carbon contact/brush on the grounding slip ring and the insulators to electrically isolate the bearings from being the spark conductor..

The insulator shim materials are available to use today's kevlar papers in various thickness' to move the bearings physical position. The movement can easily be changed by amount and angle as needed. The final bearing insulator thickness' is around .070" two half shims must total the final .070 needed. instead of .035 + .035, you could use .030 and .040 to move the COR by .010" in any angle based upon angle of shim placement.

Procedure for measuring.
In the points end of the armature there is a taper which a custom fixture for mounting a dial indicator. can be mounted. alternate is an old points
plate suitably modified for attaching a machinist "last word" gauge or similar.

To check if the added point openings are 180degrees will require a full mag assembly with a degree wheel attached.to the shaft and a buzz box or sensitive ohm meter.

More can be said and in finer detail, but the basic goal and details are spelled out .
You also need a drawer full of kevlar paper size assortment and good scissor skills.
Click to expand...

is it not easier to custom grind the cam ring ?, by altering the concentricity of the bearing in its housing you move the armature and reduce the clearance betwween it and the surrounding magnet
poles

the iron rotating core (look at any bosch power tool symbol its their logo) is made of laminations rivited together and can move a bit during the varnishing and baking process , ML cores are a nightmare as they are loose

i coat the outside and and all dowel and srew holes with silicone sealer it makes cleaning the cured baked armature a simple operation . its a bit like a toffee apple when it comes out the oven

the ends have to be match marked before dissasembly and assembled as such
mixed parts dont work generaly

the real competition mags have a few subtle differences ,stainless steel one piece drive shaft and end plate not just a knurled cheapo cast in one
usualy platinum points contacts
and finer secondary windings
slack advance cable , ie the timing wont go on to full retard if the cable should snap when youre flat out at 80mph on your 88ss and turn your exhausts red
and usualy better waterproofing and better location of the cam ring cover ,yer it has been known for the spring held points covers to fall of closely followed by the cam ring



all aircraft magneto parts are prefixed 37acx incidentaly should you find any
 
Next step:
Once the armature centerline is centered in the cam ring bore...you have a accurate and repeatable place to start. Replacing the cam ring with a good, accurate one is then repeatable. If you feel the need to work to correct a worn junk cam ring that you have the proper baseline accuracy condition to work from. Tweeking a ramp to make the opening points exactically 180 degrees opposed is of course the final goal.
If you have a worn cam ring bore, the bearing housing must be replaced. If the cam ring is worn on the OD then it should be condemned. The story of shimming the cam ring in the bore is an absolute admission that you are working with junk parts.

This worn condition is more likely in a cable advance unit that has not been adequately serviced/lubed into the felt strip sitting in the bottom groove of the bearing housing.

As a tidbit...a AA unit mag is better from a electrical performance standpoint because the electromagnetic performance does not change due to moving physical position of the armature, in a cable advance unit the points opening relationship varies withing the magnetic fields action/timing.
 
Both dynodave & desmo, very interesting but at the outer limit of my pay grade. I assume this is why there is always a search on for legitimate mag rebuilders. As the proverbial DIY I am always searching for simple solutions that can be made to work (while doing no harm) in the absence of rarer and rarer true expertise. What I take away from all comments is that on a non competition motor a degree wheel on the magneto shaft, with a hopefully concentric points cam, is a reasonably ok way to verify that the magneto shaft is centered relative to the points cam. It does seem to me, based on obsrvation, that gently pushing a loose points housing before tightening can shift the point break a few degrees, but I concede this observation may be contrary to the fixing of the shat bearings and therefore just a lucky and non repeatable coincidence.
 
TS
The dial indicator goes on the rotating device (armature) and is then measuring the distance from the cam ring bore (stationary). when the dial indicator reads the same number all around 360 degrees the shaft is then declared "centered".
From then on, the points being attached to the armature shaft now obtains the same accurate "centered" relationship that is now the COR....That relationship is not affected even if the points carrier taper is not perfectly centered to the bearing or the shaft it mounts on...

A dial indicator mounted externally measuring the shaft/slipring would only say if the slip ring is round/centered. That would have no effect on points opening therefore no effect on ignition timing accuracy for either cylinder.
 
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