R69 no spark

User avatar
schrader7032
Posts: 8147
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: R69 no spark

Post by schrader7032 »

I'm not sure I've seen a way to test the strength of the magneto "magnet". I seem to recall reading something about seeing if the rotor can pick up a wrench or something on the bench.

Have you read through Doug Rinckes booklet online? Go to the knowledge base link at the top and type "understanding" in the search box. One of the two results will be Doug's booklet.

Rereading...you replaced the ignition coil. What did you replace it with? Was it one of the older cloth wrapped coils or one of the new solid state Emerald Isle coils? The early Emerald Isle coils suffered from insufficient grounding. Vech was helpful in bringing to market version 2.0 of the coils with additional grounding.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

User avatar
vechorik1373
Posts: 81
Joined: Fri Oct 27, 2006 3:00 am

Re: R69 no spark - magneto problems and cures

Post by vechorik1373 »

Some observations and procedures I learned concerning ignition set up and problems.

1. No one ever bothers to take the body of the magneto apart and CLEAN all the surfaces that touch each other. You have a steel base to the points, mounted on a slotted breaker plate, mounted on a brass face plate, followed by 4 steel beveled washers, followed by a stack of steel plates, followed by a aluminum mounting base, held together with 4 steel screws. These dissimilar metals WILL rust and corrode eventually, and this causes the magneto body to develop a high resistance ground. When I was actively restoring bikes for customers I always disassembled the body, and glass bead blasted all the parts clean. Then I used dab of conductive, anti-corrosion grease on all the surfaces that touched each other, (including the threads of the screws) and reassembled the body. My 40 years of experience taught me that a high resistance ground will not only degrade the spark, it will cause condensers to fail prematurely. So, step one is clean the magneto body up.

2. Timing the body of the magneto is important because it will maximize the strength of the spark. You cannot kick the engine over as fast as it runs at idle, so you need all the help you can get, when kick starting.
To time the body, rotate the engine until the LINE above the letter "S" on the flywheel is in the viewing window, dead even with the stationary notch in the forward edge of the viewing window, and install the body of the magneto on the studs, with the nuts and washers. NOTICE that there is a scribed line on the brass face plate of the rotating magnet. You must rotate the body of the magneto, left or right until that scribed line is dead in the middle of the "V" notch of the brass face plate of the magneto body, and then tighten the two 6 mm nuts, and never move the body of the magneto ever again. If you run out of travel in the mounting slots of the body, this means that the rotating magnet is incorrectly mounted on the tapered nose of the camshaft. You will have to remove the rotating magnet and reposition it on the nose of the cam. Never attempt to pull the rotating magnet off the cam nose without the correct factory pulling tool!
There are aftermarket "shop" manuals (such as the Clymer manual) that incorrectly tell you to simply rotate the body of the magneto to adjust your timing. This is dead WRONG. Yes, it will change the timing, but it will WEAKEN the spark!
The breaker plate that the points are mounted on has two slotted holes for the mounting screws. They are slotted so you can rotate the breaker plate, toward the advance or toward the retard. THAT is the correct method to use to adjust your timing. If you run out of travel when rotating the breaker plate, remember this: Setting the points with a wider gap will advance the timing, closing the gap will retard the timing. The point gap (in inches is a range of .014 to .016 of an inch)

And because this is a magneto ignition, (no it's not 6 volts or 12 volts) it's a MAGNETO. The magneto ignition is a completely independent system, it does not care what voltage the bike is, or if there is a battery in the system or not. What this means is there is virtually NO voltage across the points. So the slightest bit of corrosion on the faces of the points, grease, dirt, anything, will cause NO SPARK. A new set of points, usually has a fine coating of a oily preservative on the point surfaces. ALWAYS cut a slice of a white business card, and insert it between the points and pull it through to insure the surfaces are absolutely clean. When the points close, they must make an electrical connection, or you will not have a spark!

Lets say you have now done all of the above, and installed the advance, and made sure it is seated in the slot of the shaft of the rotating magnet, and your trying to set the timing. Forget a timing light, you can check it later with a timing light, if you so desire, but you must set the timing staticlly. In order to do this, you must (if you do not have a magneto static timer) disconnect the coil from the points temporarily, and hook up an ohm meter, one lead to the little nut and bolt on the points, the other to ground. The magneto fires, when the points crack open. So place the Ohm meter where you can watch it, and the flywheel, simultaneously. Rotate the engine s-l-o-w-l-y by the crankshaft, and watch to see when the ohm meter begins to indicate the points are cracking open. This must be at the line above the letter "S" on the flywheel. You will quickly discover, how frustrating this can be, because you cannot easily access the two slotted screws that hold the breaker plate to the brass face plate, when you discover, using the meter, that the timing is off and you need to rotate the breaker plate. And if you remove the advance from the shaft, to try and adjust the breaker plate, you will discover that due to the "slop" in the fit of the advance to the shaft, it will not be exactly in the position you installed it the first time. This is why you will drive yourself insane. The trick is to not tighten the two slotted screws that hold the breaker plate on, excessively. Just snug them lightly. Then, using a flat punch and a light hammer, place the end of the punch way out on the upper or lower edge (depending on which way you need to move it to bring it into time) and using the hammer on the punch, tap on it, to rotate the breaker plate, while the advance is mounted and TIGHT on the shaft.
Vech
Technical Adviser, Former owner, Bench Mark Works
662 312 2838 cell 9 am to 4pm CST PLEASE!

User avatar
jwonder
Posts: 547
Joined: Wed Nov 23, 2016 7:50 pm
Location: Long Island, New York
Contact:

Re: R69 no spark

Post by jwonder »

And that post from Vech is GOLD!!!

Thank you Vech!!!!!
James Wonder
Long Island, New York

andybee65
Posts: 16
Joined: Sat May 14, 2022 9:56 am

Re: R69 no spark

Post by andybee65 »

Thank you very much for this very detailed explanation. That his given me a true insight as to setting everything up. Think I'm going to be busy for some time now!

andybee65
Posts: 16
Joined: Sat May 14, 2022 9:56 am

Re: R69 no spark

Post by andybee65 »

I replaced the coil with an older style material type. I have spoken to a chap here in the UK who has suggested that may be at fault, as when I kick the engine I read about 6 volts hitting the primary winding of the coil(Which I am told is about right), but I also only get this voltage on the secondary winding. I have just placed an order for the type you describe(with the additional earth connection). I am going to try that before I strip down the magneto set-up. Fingers crossed!

andybee65
Posts: 16
Joined: Sat May 14, 2022 9:56 am

Re: R69 no spark

Post by andybee65 »

I replaced the coil with an older style material type. I have spoken to a chap here in the UK who has suggested that may be at fault, as when I kick the engine I read about 6 volts hitting the primary winding of the coil(Which I am told is about right), but I also only get this voltage on the secondary winding. I have just placed an order for the type you describe(with the additional earth connection). I am going to try that before I strip down the magneto set-up. Fingers crossed!

andybee65
Posts: 16
Joined: Sat May 14, 2022 9:56 am

Re: R69 no spark

Post by andybee65 »

schrader7032 wrote:
Sun May 15, 2022 12:57 pm
I'm not sure I've seen a way to test the strength of the magneto "magnet". I seem to recall reading something about seeing if the rotor can pick up a wrench or something on the bench.

Have you read through Doug Rinckes booklet online? Go to the knowledge base link at the top and type "understanding" in the search box. One of the two results will be Doug's booklet.

Rereading...you replaced the ignition coil. What did you replace it with? Was it one of the older cloth wrapped coils or one of the new solid state Emerald Isle coils? The early Emerald Isle coils suffered from insufficient grounding. Vech was helpful in bringing to market version 2.0 of the coils with additional grounding.
I replaced the coil with an older style material type. I have spoken to a chap here in the UK who has suggested that may be at fault, as when I kick the engine I read about 6 volts hitting the primary winding of the coil(Which I am told is about right), but I also only get this voltage on the secondary winding. I have just placed an order for the type you describe(with the additional earth connection). I am going to try that before I strip down the magneto set-up. Fingers crossed!

User avatar
wa1nca
Posts: 971
Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma

Re: R69 no spark

Post by wa1nca »

Quote from Vech:
(if you do not have a magneto static timer) disconnect the coil from the points temporarily, and hook up an ohm meter, one lead to the little nut and bolt on the points

What a PITA to remove the point wire with the small bolt and nut

I like the coil sold by Max BMW with the point wire connected to screw part of terminal that connects the kill wire from the ignition switch so you dont have to disconnect it with the small screw on the points and can just unscrew it from the kill terminal screw
12138004104_1_B.jpg
All coils can modified like the one shown
Just cut the old point wire from the bottom of the kill terminal tin it and then connect it to the screw terminal with the kill wire

Tommy
Tommy Byrnes
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US 75 R75/6
Ashfield, Ma
USA

User avatar
kingcowie
Posts: 60
Joined: Wed Oct 28, 2020 1:29 pm
Location: Wollongong

Re: R69 no spark

Post by kingcowie »

Awesome post,, thanks Vech.
Shane
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project

User avatar
vechorik1373
Posts: 81
Joined: Fri Oct 27, 2006 3:00 am

Re: R69 no spark

Post by vechorik1373 »

One more thing I will say, concerning magneto coils, is that after 24 years in the parts business, my first hand experience is:

ALL the rewound coils that come out of Europe, have a high failure rate. Don't waste your money on them.
And there is NO warranty on them.

I had NEW coils produced, made by Emerald Island. These coils, with a plastic enclosure, have windings that have been potted under a vacuum. They also have an external ground wire on them. The most important thing, is that I warranted them for one year. I sold 1000's of them over the years. With very very few failures. What does that tell you? THAT THEY ARE RELIABLE.

And, a explanation as to why original coils fail eventually.
BMW magneto coils are really a Siamese coil in the sense that they have one primary winding, and TWO secondary windings, one for each spark plug. Each secondary winding has 10,000 turns of enameled copper wire in them. The enamel IS the insulation. Now, in service on a BMW engine, the coil is exposed to fairly high temperatures when the engine is running.

What does copper do, when it is heated? It expands. What does it do when it is cooled? It contracts. Over many, many cycles of heating and cooling, eventually, the enamel insulation will be chaffed off, so when it gets hot, it begins to short out.
That means less than 10,000 turns of wire are doing the job, and the spark begins to weaken.
It will keep on working, because remember, the FASTER a magneto turns, the STRONGER the spark gets.
But, when you shut it off, and attempt to restart a hot engine, with a partially shorted out coil, it won't produce a spark because you can't even come close at kick start speed, to the speed the engine runs at, at idle.

And many times, with an original coil, when the engine becomes dead cold, (the windings shrink, remember?) it will have broken the short and the spark will magically return. That is the classic symptom of a failing coil. And through time, it will get worse and worse and get harder and harder to start, until eventually, it will fail altogether.

So, the lack of spark you are experiencing, is that maybe you have a rewound coil, and just because it is "new" doesn't mean it is a good functioning coil! Remember, the word assume, is made up of ass of U and me! :lol:
Vech
Technical Adviser, Former owner, Bench Mark Works
662 312 2838 cell 9 am to 4pm CST PLEASE!

Post Reply