a little help from BS expert please.

[Terry H]

Can a magneto on a Briggs mower motor just die with no visual signs? I get no spark, but get reading of 4.5k ohms from plug wire to gnd. Any help would be good...Chief

 

[Mark42]

Re: a little help from BS expert please.

Chief,<br /><br />I am not familiar with the actual resistance value of the coil, so I can't comment on your reading. <br /><br />But having worked on these beasts for many many years, I can say that chances are the points are burned or the condenser is bad or the little push rod that follows the cam on the crank is stuck up holding the points open. <br /><br />Remove the flywheel and replace the points and condenser first. Before you replace the cover, you should be able to get a real good spark by just twisting the crank so the magnets pass over the coil. Just remove the spark plug so there is no compression to mess you up. Properly gapped points should fire the plug with just a twist of the hand.<br /><br />Don't forget to tighten up the flywheel nut (pull starter clutch thing) with a few blows of a hammer using a wood block against an ear of the flywheel nut. Failure to do this will shear off the aluminum key. The key is just there for alighment purposes and is not intended to prevent the flywheel from spinning on the crank. So tighten it up!<br /><br />Good luck!<br /><br />Mark<br /><br />PS I have never seen a coil go bad, its always the points/condenser or a short in the "off" circuit that grounds the points.

 

[Terry H]

Re: a little help from BS expert please.

I think you hit it right on, I just could not find a problem with the magneto...thanks, Chief

 

[jimr]

Re: a little help from BS expert please.

Oh I thought you ment B...S...

 

[Terry H]

Re: a little help from BS expert please.

Mark, I hate to tell you this but the points were just plain missing, same with the condenser. Actually there weren't none, and if I hadn't read your reply with such overambitious hopefullness I would have known. Anyroad I now have spark, now to replace the plug I broke and make sure it weren't really a fuel delivery problem. Thanks, Chief

 

[Terry H]

Re: a little help from BS expert please.

jimr, I said "BS" cause it's a lawnmower and I gots to run it and I gots to fix it and I got better things to do...Chief

 

[Mark42]

Re: a little help from BS expert please.

Glad to hear its running. I take it you weren't the one to remove the points, right? Someone give you a free-be mower?<br /><br />Regards,<br /><br />Mark.

 

[Terry H]

Re: a little help from BS expert please.

Mark, this mower is a couple of years old, I bought it new, the mowor has a 6hp ohv BS engine, and the only wires hooked to the magneto are the plug wire, and the ground-out wire. the magneto/coil is one unit and it's a single winding. There's nothing under the flywheel. Anyroad it's not running yet, cause I didn't put it back together yet. With a spark plug I can test whether or not it runs, and when it's running I will reassemble and mow my knee-high+ lawn. Chief

 

[cajun555]

Re: a little help from BS expert please.

Its got whats called the Megatron ignition. No points or condensor. My 20 year old 3hp is the same way. Sure makes maint. simpler.

 

[demsvmejm]

Re: a little help from BS expert please.

I have seen a spark plug spark when out of the cylinder. Everything looked just fine, but put the plug back in and nothing. Replaced the plug and the thing fired right up first pull. No guarantee, just my experience.

 

[Terry H]

Re: a little help from BS expert please.

All looks fine, but I have to guess that the faster the flywheel turns the hotter the spark. When I put this thing together I just cannot see a spark when l tug on the chord. I set the magneto about .010 from the flywheel, That's about where it was. I set the new plug at about .030. Everything appears ok, it just don't start. This is just way too simple for it not to work...Chief

 

[eurolarva]

Re: a little help from BS expert please.

When checking for spark the plug tip needs to be grounded. Make sure the kill switch is working correctly. I have taken these apart before and usually my lack of spark is the kill switch is grounding the ignition system and it wont fire.<br /><br />If you cant figure it out try here<br /> Lawn mower repair forum

 

[Terry H]

Re: a little help from BS expert please.

I didn't have a problem with the grounding or the kill switch, just that the spark is so small I couldn't see it. I finally hookied the flywheel nut up with an impact wrench and got it turning fast enough to make a big spark that I could see. Anyroad, not to worry, I got it running. Carb full of debris...Chief

 

[dogsdad]

Re: a little help from BS expert please.

I went round and round with that type of B&S ignition last fall. I replaced the magneto twice with parts from a place I found on-line. Both parts failed in short order. They were cheap foreign made junk. I got fed up and bought a new John Deere lawn tractor. <br /><br />In the meantime, I asked the vendor to just return my money because I wanted a genuine B&S part. Instead, he sent me a B&S part. I installed it and the tractor ran fine. But I didn't need it anymore.<br /><br />My wife and I had seen our neighbor across the street cutting her one-acre plus lawn with a push mower, and we felt bad for her. I took the B&S machine across the street and gave it to her, and it runs fine to this day.<br /><br />The moral of the story is "use a Briggs & Stratton part or you'll likely be replacing it again soon."<br /><br /><br />-dd-

 

[Terry H]

Re: a little help from BS expert please.

I don't disagree with that dd. It's not starting again today, I wonder, but can't imagine, if that magneto can be intermittent, or maybe I just need a new carb. Chief

 

[ED21]

Re: a little help from BS expert please.

I had a magneto go bad on a kohler engine. It was intermittant for a long time until it just quit.<br />Your description of the problem, including no points was exactly like mine.<br />.010 is what the gap is on mine.

 

[dogsdad]

Re: a little help from BS expert please.

Chief, when I had the problem with the original magneto it was indeed intermittent. It would work sometimes, and sometimes it would not. The cheap foreign-made replacements, however, seemed to never work again, if I recall correctly, after they failed.<br /><br />A matchbook cover or notecard is about right for setting that gap, by the way. It should be set with the magnet on the flywheel under the pickup coils of the magneto.<br /><br />I will also add that I seem to recall having problems seeing the spark with the plug removed. No idea why that is.<br /><br />I'll betcha the magneto is the problem!<br /><br /><br />-dd-

 

[Terry H]

Re: a little help from BS expert please.

That is got to be the simplest ignition system there is, I just find it dificult to believe it can be intermittant. If the machine continues to give me grief, I'll just have to get another magneto. Plenty of BS dealers around so I don't see getting a part as being a problem. Chief

 

[dolluper]

Re: a little help from BS expert please.

Chief if yours has a magnetron ign there is a replaceable module on the back of the armature if not you have points and condensor which will be located behind a plate cover above your drain oil fill ,crank level two bolts on cover it's a breaker box

 

[Terry H]

Re: a little help from BS expert please.

Well it started again, and again without the guv. I mowed with it anyhowz, and 1/2 hour in to mowing the guv kicked in so for now it's running quite well. Dolluper, there are no wires to the magneto so I can't see what points could possible do, and no replaceable module on the mag either. It's magneto to sparkplug and that's it. Any hows I have about 10% of my lawn mowed, if it starts again I will finish by the weekend. Chief