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ignition timing #753348
10/19/18 2:22 pm
10/19/18 2:22 pm
Joined: Aug 2009
Posts: 1,000
gastonia .. NC
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limeyrider Offline OP
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gastonia .. NC
I have been trying, without success so far, to balance the ignition timing on my 1966, 650 SS. I have set the ignition timing on the drive side ..per the manual , except I use 28 deg. and not 32 deg., I have the timing spot on at 28 deg.on the drive side, when I check the timing side timing the points do not open until 19 deg. BTDC ??.
I use a piston stop to establish TDC on the drive side, set the points at 28 deg. BTDC, then without changing anything else I rotate the motor through 360 deg. and check the timing side.
I have gone around and around checking the cam ring .... I measured an error of 5 deg. between the cam lobe spacing... don't understand how that translates to a 9 deg. error in timing.

If anyone can spot something that I may be missing or doing incorrectly ... please feel free to jump in !.

I have to give a shout out to Skip Brolund for all of his help and patience in trying to get this sorted .

Thanks for any and all help / advice.

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Re: ignition timing [Re: limeyrider] #753350
10/19/18 3:41 pm
10/19/18 3:41 pm
Joined: Aug 2001
Posts: 7,634
scotland
triton thrasher Online content
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scotland
Of course a cam lobe variation of 5 degrees gives you a crankshaft variation of 10 degrees!

Think about it.


Then fix it. Some of us grind the lobe. Some shim the edge of the ring with feeler steel (if an auto advance magneto). Some tilt the points housing with shims at one corner screw.

Some people even try another cam ring.


Amateur Loctite enthusiast.
Re: ignition timing [Re: limeyrider] #753374
10/19/18 9:20 pm
10/19/18 9:20 pm
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Posts: 2,341
Oztralia
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Rohan Offline
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Yes, the magneto spins at half engine speed, so any degrees of error in the maggie are doubled at the crankshaft.

Have you checked the points gap for each side of the maggie.
If the difference is minor, the manual sez to split the difference.
If the cam ring is heavily worn, which sounds like the case, maybe Skip needs to offer you a new one ?

Its maybe also worth checking the magneto chain is correctly adjusted.
Any large amount of slop can add to timing errors, particularly if you concentrate on only one side of the spark
and leave the other to its own devices...

Re: ignition timing [Re: triton thrasher] #753375
10/19/18 9:20 pm
10/19/18 9:20 pm
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gastonia .. NC
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limeyrider Offline OP
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Thanks Triton Thrasher .... still scratching my head ..... but I will get it sorted.

Re: ignition timing [Re: limeyrider] #753377
10/19/18 9:25 pm
10/19/18 9:25 pm
Joined: Aug 2001
Posts: 7,634
scotland
triton thrasher Online content
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Sometimes new cam rings are purchased and it doesn’t fix the problem.


Amateur Loctite enthusiast.
Re: ignition timing [Re: limeyrider] #753380
10/19/18 9:44 pm
10/19/18 9:44 pm
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Oztralia
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Rohan Offline
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I well know that story.
My 1st dommie I bought had a K2F that was less than pristine, shall we say, although it would run.
Even though the end containing the cam ring was visibly moving (!)
Cobbling together the remains of 3 x K2Fs gave a reasonable workable maggie,

its surprising how many faults can accumulate with the miles.
Making sure that everything is Concentric to each other and solidly bolted down is a large part of the cure.

Re: ignition timing [Re: limeyrider] #753392
10/19/18 11:56 pm
10/19/18 11:56 pm
Joined: Sep 2007
Posts: 1,133
Ottawa, Canada
gREgg-K Offline

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Limeyrider, the sort of timing (side-to-side) error you're experiencing is very common with our aging K2F mags, especially after years without maintenance.

Before you go too far with trying to repair it, be sure you diagnose the root cause: otherwise, as Triton Thrasher says, your problems will continue.
It all comes down to careful testing and meticulous assembly, and many times there is not one fault, but an accumulation of errors causing the problem.
Persevere, though: it's well worth getting it right, because precisely timed sparks are fundamental to the smooth running of your engine.

... Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
Re: ignition timing [Re: Rohan] #753436
10/20/18 2:32 pm
10/20/18 2:32 pm
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gastonia .. NC
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limeyrider Offline OP
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Thanks Rohan .... there was a significant difference in the points gap ... .012" drive side, and .007" timing side, I ground some material off the OD of the ring .... opposite to the side with the error, I put a .005" shim under the OD of the ring ... opposite to where I had ground material off, this seemed to help narrow the difference ....I still got some error .... .012" and .010".
In preparation for some more investigation I took the cam ring out, removed the shim and set up a degree wheel, more head scratching .... using the degree wheel and a multi meter set up I now show no error in cam lobe spacing .... I will be taking a much closer look at the results of that test .... as you all will have surmised ...I am NOT an expert in the field of magneto investigation / repair .... but I really would like to get this problem solved myself .... just for the satisfaction .... (and I don't have a budget for expert repairs).
The mag. drive chain is adjusted to give 3/16" to 1/4" up and down movement.

The magneto in question was , as I am told by the PO... sent to the UK for rebuild through a motorcycle repair shop that he was dealing with , the PO has no idea what work was actually done ... new armature, field and capacitor ??,certainly NO new cam ring.

Re: ignition timing [Re: limeyrider] #753454
10/20/18 9:11 pm
10/20/18 9:11 pm
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Oztralia
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Rohan Offline
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Something which is worth checking with an old magneto (but shouldn''t be necessary with a new armature ?)
is to chuck the armature in a lathe, and make sure it is straight and true. If its banana shaped, like some seem
to be, the points will waggle all over the place, and it is nigh impossible to get the maggie to fire evenly side to side.
Don't forget to fit a 'keeper' to the body during this, or the magnetism can evaporate.

Its also worth checking that the points will bolt to the end of the armature nice and square. If its a sloppy or
tilted fit, it will also be difficult to get even firing. I've used valve grinding paste to firm up the fit here, although
I don't know if this is recommended or not.

Something else I have seen is that the little alloy housing that holds the camring do not all seem to be the
same - some appear to be more or less Concentric with the armature than others. When you can change
just this component and things improve, greatly, you know that not all components were created equal... ?
Where the shimming comes into it ?
hopethishelps.

Re: ignition timing [Re: Rohan] #753465
10/20/18 11:03 pm
10/20/18 11:03 pm
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gastonia .. NC
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limeyrider Offline OP
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Thanks Rohan .....

I don't have access to a lathe now, I did put a dial indicator inside the tapered bush that the points fit into, I ran the mag. spindle using a drill, the bush ran concentrically .

I put some bluing on the points plate taper and the tapers appear to mate well. The key is in good shape also.

The points / cam ring housing was .002" out of round, but I heated it , squeezed it VERY carefully and got it back round again. I loosened the two corner mounted screws about a half turn and tried moving the whole housing by shimming different points , nothing helped there, I get a consistent 5 deg. error .... it looks like the cam ring is the culprit .... based on my rudimentary testing anyway..

The cam ring looks like it has got some miles on it, lack of lube over the years possibly ???.

Thank you for your interest and comments.

Re: ignition timing [Re: limeyrider] #753468
10/20/18 11:30 pm
10/20/18 11:30 pm
Joined: Sep 2007
Posts: 1,133
Ottawa, Canada
gREgg-K Offline

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Limeyrider, if you suspect one lobe on the cam ring being worn more than the other, try pulling it back off its locating peg, and rotate it 180 degrees. Now, if you find the timing error reverses sides, you've pretty much proven it is due to the cam ring.

.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
Re: ignition timing [Re: gREgg-K] #753482
10/21/18 2:26 am
10/21/18 2:26 am
Joined: Aug 2009
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gastonia .. NC
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limeyrider Offline OP
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Thank you Gregg... good idea !, as the ring only has one locating slot it did not occur to me to rotate the ring through 180 deg. !.

Thanks again,

Re: ignition timing [Re: gREgg-K] #753516
10/21/18 7:33 pm
10/21/18 7:33 pm
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gastonia .. NC
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limeyrider Offline OP
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I'm not sure what this tells me ... if anything .... I checked the cam lobe spacing with the cam ring in it's normal position .. setting the degree wheel at 0 deg. with the points opening on the drive side position , I rotated the armature shaft until the points began to open on the timing side, the reading on the degree wheel showed 175 deg..
I took the cam ring out and reversed it's position and then I repeated the procedure , began with the points opening on the drive side 0 deg. on the degree wheel, turned the armature shaft until the points began opening on the timing side , the reading on the degree wheel was 170 deg ????

Re: ignition timing [Re: limeyrider] #753524
10/21/18 9:20 pm
10/21/18 9:20 pm
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Rohan Offline
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Again, what was the points gap on each side of the cam ring ?
Is the heel of the bit that rubs on the cam ring nice and square, and the cam ring square across the whole surface.


Re: ignition timing [Re: Rohan] #753549
10/22/18 12:37 am
10/22/18 12:37 am
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gastonia .. NC
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limeyrider Offline OP
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Hi Rohan .... the points gaps are ..... drive side .012" and timing side .010", the shoe that runs on the cam ring is square, the points assembly looks to have been very recently replaced. They started out at .012" and .007" respectively.

I have not verified that the cam ring is square across the operating surface.

I contacted the shop through who the magneto was rebuilt .... I was informed that Doug Wood did the rebuild, Doug has a very sound reputation in the USA, apparently the cam ring was not replaced at the time of the rebuild .... don't know why.

Re: ignition timing [Re: limeyrider] #753592
10/22/18 1:22 pm
10/22/18 1:22 pm
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Ewing. NJ
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edunham Offline
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Doug is a good guy. Contact him and I am sure he can help you out. My Atlas had a similar issue. Part of the problem is that the mag is made up of a number of assemblies that are supposed to all fit together perfectly concentrically. with worn casings, bearing wear, old threads, replacement parts, etc., it's pretty miraculous if they do. Add an imperfect cam ring, and its even more of a miracle. I live near enough Doug that I took my mag to him in person. Ultimately, he skimmed the outside of the cam ring (my bike has an AAU), and wedged a shim on one side to make the points plate Concentric. The result was the 2 cylinders firing within a half a degree of 180 degrees. It transformed the way the bike ran.

Ed from NJ

Re: ignition timing [Re: edunham] #753593
10/22/18 1:45 pm
10/22/18 1:45 pm
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gastonia .. NC
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limeyrider Offline OP
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Hi Ed .... do you have contact info for Doug ....I'd like to call and talk to him .

Thanks.


Cancel that Ed.....I found some contact info on Doug.

Last edited by limeyrider; 10/22/18 1:58 pm.
Re: ignition timing [Re: limeyrider] #753597
10/22/18 2:06 pm
10/22/18 2:06 pm
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Hamilton, Mass. USA
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Dave Comeau Offline

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Re: ignition timing [Re: limeyrider] #753643
10/22/18 9:15 pm
10/22/18 9:15 pm
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Oztralia
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Rohan Offline
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While that is an excellent and ultra detailed account of restoring a magneto,
it is probably fair to say its far too detailed for what most folks need to easily
find to deal with the recalcitrant K2F they have in their hand ?

A good editor would weed out all the ultra detail, and leave just the basics. ?
Say as a magazine article would do.
Or arrive at a good 5 or 6 paragraph summary ?

The index almost does it already - with some helpful comments/detail it may suffice.
I've got some time coming up divorced from my bikes, I'll look into it.

P.S. I've probably got a dozen K2F's in my collection, and I found from my schoolboy
days (with then zero knowledge of the theory of them) it was relatively easy to
selectively assemble a good working maggie from used parts.

If you spin them and strobe the timing, it is not too difficult to figure out where they
are not correct, as we have just seen with this thread here.
Just weeding out the banana shaped armatures, bad threads, loose fitting items
and dry bearings, worn slip rings, poor seals and knackered brushes, what was left
gave something approximating what a fairly good maggie from Lucas would have been.

I find it a little bizarre though that newly 'rebuilt' maggies can still have these faults -
the local maggie rebuilding guy here runs all newly built maggies for hours with a
heat gun on them and strobes the timing, so you know you genuinely have a brand
new Lucas instrument ready for another lifetimes work. But you sure pay for it....

Its also worth commenting that the Lucas manual recommends a yearly service for
all Lucas Magnetos, including a good clean inside, AND regreasing the bearings.
How many get that these days, we wonder....

Re: ignition timing [Re: Rohan] #753658
10/22/18 11:12 pm
10/22/18 11:12 pm
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limeyrider Offline OP
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I am stepping back to square one with regard to my K2F magneto, although I have come " close ", I want to make this magneto as good Joe Lucas intended, if I can.

I have located a neighbour who has a small lathe and is willing to allow me the use of the machine.

My intention is to bore and sleeve the end points housing .... I will be locating from the bearing bore so as to preserve / restore concentricity, I intend using the old cam ring until such time as it is proven to be junk.

A conversation with the shop who sent the mag. to Doug Wood for rebuild tells me that the mag. has a newly rewound armature, field, capacitor and new bearings ( 1500 miles have been added to the bike since the mag. rebuild ), after replacing all of those components I am wondering why the old cam ring was re -installed.

In the absence of a " keeper " , as advised by Rohan, I am going to assume that the armature is NOT " banana shaped ".

Hopefully, machining and careful assembly will pay a dividend .

As I had planned, I have machined the contact breaker housing and inserted an aluminium sleeve ....030" wall thickness.
I located the housing from the bearing bore mounted onto a stub machined on a piece of square aluminium bar, stub dia. was .0001" under the bearing bore dia., the housing was held in place using the two corner holes and 10 - 32 x 1 1/2" cap head screws. I measured the cam ring OD and added .060" to that dimension , I bored the cam ring housing to that dimension. Leaving the housing set up in the four jaw chuck, I removed that set up from the lathe and put a three jaw chuck on to turn and bore a piece of aluminium bar to make the ring insert, the ring was light press fitted into the cam ring housing and the set up put back on the lathe for final skimming of the bore to fit the cam ring. After the inserted ring was finished to size I took the housing off, re -machined the square bar to form another boss to accept the cam ring insert bore, using the corner bolts as before I took a very light skin cut across the mounting face of the cam ring housing .... it was off square to the cam ring bore by .002". After all of that was finished I re assembled the housing onto the mag, body, re-installed the cam ring and points plate .... checking the contact gaps .... both are now equal at .012", checking the cam lobe spacing with a degree wheel and multi meter I now have 180 deg. .... checked at ten full rotations of the mag. armature shaft.
The mag. is back on the bike awaiting setting of the ignition timing .... hopefully I will get 28 deg. BTDC on each piston !! .... if not ..... electronic ignition is next smile


I set the ignition timing today, set 28 deg. BTDC on the drive side, I got 27 deg. BTDC on the timing side, I turned the motor over several times through 360 deg. and checked each cylinder. I used two different timing discs and got the same results.
I used cigarette paper in the points to indicate the opening point .... in his book , Paul Dunstall recommends using a battery and bulb ( taking out the points centre bolt ) but I did not trust the taper to hold the points sufficiently well.

I am happy with that result .... perhaps not perfect .... but a whole lot better than it was.

Thanks for the help and advice.




Last edited by limeyrider; 10/30/18 7:46 pm. Reason: adding notes

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