B&S Ignition


Staff member
Well, I got back to this again. What the link Nickb2 posted reminded me of was an "inconvenient truth" I am prone to ignoring: magneto systems have not only the flying-magnets and coil, but must have some sort of "breaker-point" arrangement. I don't understand how that works with a mag system, so tend to ignore the need to interrupt the coil primary. I kid myself that the primary is only used as a means to kill the engine, by shorting it out. The coil on this engine is the "integral" type, with the primary triggering module buried in the coil. Alas, B&S calls this system "Magnetron". If you search for that term you have to wade through quite a bit related to microwave oven magnetron tubes...

Previously, when I thought there was only the plug, coil, and magnets, I had replaced both the coil and plug and was thinking the problem must be bad magnets, as unlikely as that seemed. I even toyed with the idea of trying to charge the magnets. Now though, I am reminded that the electronic triggering in the coil assembly could also be bad. In fact, reading resistance across the primary (on both old and new coil) shows that same low resistance now matter which polarity I use for the meter leads; as if they were just simple windings. I would expect that resistance would be different depending on polarity, since there is some active electronics in there. Worse yet, sometimes the new coil does show a difference, like ~1 ohm vs. hundreds of ohms, but it is frustratingly inconsistent. Can that be possible, or is there something flaky about how I am connecting the meter? Oh, wait, that is how the engine is acting, intermittent...

Could it really be I bought a bad coil? I got it from a long-established B&S dealer, but that may not mean anything. They won't allow me to return any electrical parts, because any damage I do to them won't be visible. But, I bet that policy doesn't apply to their service techs as they "throw parts" at a problem in the shop.

I would like to prove conclusively what is going on here, even if just for my own peace-of- mind. (Mowers are too inexpensive to make this effort practical!) I'm thinking now of opening up the old coil to repair/modify the interrupter circuit and prove the magnets and coils are OK. Anybody have good info on what is actually inside those coil assemblies?


Wrench. I help when I can
I understand your questioning. I myself have looked at certain items in my life and was as hard headed as could be.

The last stint where my GF told me to "lache prise" which means "let it go". I just could not. It was my stove. The selector switch had melted and caused the fuses to blow. I then proceeded to order the part, (which btw took some cleaver google research) just to get a wrong pin switch and my GF had lost the receipt.

No taking back that switch. 60$ or so down the drain. I refused to chuck that selector switch in the garbage. I took out my multi meter and rerouted power from the timer to the lacking pin and now I just use a dollerama timer to cook my chicken or lasagna etc.

Any brainless person or one with a full bank account would have said "buy a new stove"

Why would I buy a new stove when I know all the incipient parts work?

So I understand what you are saying. If I was you, I would be irate and fussing and fuming until said mowers work like they should.

Fundamentally, I think this is what makes a good technician/problem solver be soo good at his or her job. The NEED to KNOW why!!!

It is not really about how much it costs, more the why did it stop functioning the way it was designed to do so.

I could not copy/paste the Briggs and Stratton link, it is copyright.

But worth a read, you seem to be THERE so to speak.

I will post that link again, well worth the read. Something VERY simple is eluding you here and I know it is knackering at your heels like a snarling small dog that doesn't know it might have bit off more than it can chew.

For your honor, I want both of those B/S's to run just for the sake of your sanity.



Wrench. I help when I can
On a funny note, I made $ today. It was so funny I could laugh. Sold my shark steamer for the price I wanted at the next door neighbors side walk sale, and got 4 couch feet and a new back pack to boot.

The shark steamer thing is only good for vapor and trying to get creases out of clothes or whatever. I had no use for it.

But the 4 "merisier" feet cost almost 20$ a pop brand new at Home Depot.

I lost everything in my divorce. I am slowly getting back to where I should be. And that is greatly due to you all here.

Never underestimate the power of the written word.



Wrench. I help when I can
Jack, you just opened a can of worms.

When I was learning my English in southern Ontario, close to Niagara Falls. I kissed a girl named Peggy. I brought her to a movie. The only thing I remember was me trying to grab her hand in the pop corn and feeling so awkward it was nuts.

I must say, I did get a full kiss later on, and my father was late to come pick us up. I think he did that on purpose.

I had stars in my eyes, until I had to move back to Quebec. I think I was 12 or 11 yrs old.

I remember walking her to school. I would shoo away my dog just to take her books.

Amazing how old memories bring us back to the basics in life.

Bill in so many words without saying his wife's name, has said that he is a very happy camper.

Bill has inspired me alot. In his writing I see a very profound soul and a generosity that is nice to see in this dirty world.

I think the term I am looking for to say what I feel about all the guy's here, is that we have a certain connection, a kindred spirit.

My current GF just called back from montreal. All I could hear in the background was greek. The greeks have a particular way of expressing themselves.

They seem to argue all the time, but my GF tells me that is how they talk to each other. All is good.

I am not willing to learn greek. If I have to argue over someone for a parking space or such nonsense, the Quebecois comes out.

I do not want to spark a debate, but us frenchman have been ostracized for a simple matter of land and language.

Politics aside.

I am Canadian first, and French Canadian to the hilt.

So when I meet others from other places that do not understand, I simply say, I am a French Canadian and damn proud of it.

It is my responsibility to learn english as I realize most of our great country is a majority english.

What sucks is the ignorance of others from the other provinces. I fought physically many time just because I spoke french in Toronto, or Manitoba, etc.

I was not proud of my country when the blows fell down.

But I must say, the pride of a Quebecker is second to none. We are renowned for a very tough ppl and mostly liked across the globe.

And if that TV guy actually get the presidency, I am sure glad I am still a part of Canada. If he does get it, you can pretty much say he bought it.

Politics and boob tube. Where is this freaking planet going?


Staff member
Just for the record: I have this flywheel mounted in a lathe, so I can "crank" as long as I want, with the coil on a bracket that can easily be set to any air-gap. At 860 rpm the spark is there, but iffy. At 540 rpm spark is rarely there. And, this is at atmospheric pressure; compression pressure would prevent any sparking, I'm pretty sure. I tried the screw-driver test for the magnet(s). It holds on the center magnet, but not the outboard ones. Of course, B&S just speaks about the magnet, not all three...

Oh, and the "no carb" one is easy to diagnose, the float-needle leaks. I screwed-up the seat for it (a soft rubber doughnut) and haven't figured out a suitable replacement yet. I wish the carb on "no spark" would fit "no carb", but it would take a bit of fussing. I think the coil on "no carb" would fit "no spark", but the screws (#8/4mm) holding it are rusty enough that they won't budge with normal effort; I'm afraid I'll twist them off leaving their stumps in the "no carb" crankcase.
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Wrench. I help when I can
Yep, Bill is a busy boy.

I would not have thought of using a lathe to consider spark consistency.

This provokes me to an older memoir. The garage had bought a brake disk on vehicle I tried it only twice and hated that damn thing.

When the lift went side ways, the cutters bore way to far.

I asked the boss why did you buy this POS? He said the other techs are costing me too much money with the old brake disk and drum Ammco.

I must say, I kept a few cutters in my tool box just because of that. I could surely bet some idiot had burned the diamond cutters because the coffee break was close to hand.

The dude that came to the shop to show us how to work this contraption.

I found a very similar video that I wasted my lunch break on. I don't think this idea made a billionaire out of somebody.



Staff member
I have been away all day, but here is an update:

Yesterday I checked the mag out again on the lathe, and everything seemed fine. I even lowered the speed down into the 300 rpm range and the spark was good. So, I put it all back on the engine and it started on about the first pull. She used it for another hour or so with no problem. Well... one problem: I left the "kill" wire off (had removed it previously to eliminate that as a problem) so she couldn't stop the engine. I had to stifle it by removing the air filter and putting a plug over the carb intake. I'll let her try putting some more time on it tomorrow. If it is still alive after the next session, I'll put the kill wire back on.


Wrench. I help when I can
Aha. the mysteries of life. So cleaning the rust off those magnets was the solution?

So at least 1 is running now. Your son will be happy!
Really? Oh well, "cleanliness is next to Godliness"

Sure hope that is it. All the way from no start to no shut off in one easy step.


Staff member
No, I didn't clean anything before it looked OK on the lathe... just a new day. I'm curious to see how it goes today!


Wrench. I help when I can
Well, then my reasoning behind this is that you provoked a good action by actually removing some parts and just probably provided unwittingly a proper ground.

I think I wrote this here before. I chased a no start on a nissan maxima or altima (can't remember but I know I hated that white paint job, I only really remember wanting to scratch the paint up and down) to no avail and was ready to throw the gloves. I worked on that car for days on end.

I was so confused, I even tried a new ECM and my gut was still saying it was not the proper way to go.

When I called the nissan tech line, the guy on the phone told me to remove the transmission. I said why. It is just a bad crank sensor reading. I will trace the wiring. 3 days later I called him back. He was right. The bell housing had corroded enough to cause a bad ground.

Before even delving into that guy's theory, and looking at 12 hours of labor for a bad ground, I even tried a 18 wire gauge
ground strap between the engine block and the tranny. Still no go. I was completely stumped.

An old wolf at the shop even tried to help me and he was equally stumped as I was. His nickname was "Mozart". He was wizard when it came to this kind of stuff. A bit like me. My nickname is "TAZ"

Anyway, just the action of removing the lower structure, and cleaning all available surfaces with my zip gun and 3m pads to a more than perfect mirror polish was what did the trick.

All the guys in the shop came to the car and when I turned the key, wham. It started like a gem.

We all were flabbergasted it actually ran. A few of the tires guy's asked me what did I do?? I said some guy on the tech line told me that some technicians had come across this same issue and they were working on a TSB for this particullar problem, but it was not published yet.

The weirdest thing was that the ecm would actually pulse the injector pattern. You could hear the injectors clicking away in their pre programmed way, and still the ECM thought it was actually running. It would flood the engine so bad I had to replace the engine oil 3 or 4 times.

I came home one night and my ex wife asked me that night, why are you pretty aggressive. I don't really take my work stuff home. But she could feel that something was wrong, because I had run out of solutions on this car.

This problem cost the client more than he could pay for it. I was happy to see him drive off. I said please only come back for regular maintenance. If I ever see you come back with that check engine light on for a no crank condition, I will purposefully tow that car to the wrecking ball and smash it to smithereens. He actually left a 20$ tip.

Everybody was clueless. Who would have imagined that only on the manual trans and not the auto that this grounding issue was causing grief to a few tech's out there.

Some genius out there found the solution, warped is it may sound.


Wrench. I help when I can
Try to explain that to a paying customer.:eek:

I have to remove your transmission to create a proper ground. I might as well be speaking in martian or chinese. The garage even provided him with a loaner. He asked if he could keep the loaner car. Yeah, no go.