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Discussion Starter #1
I have a B&S 10 hp Easy Spin, model 243431 that has no spark. Checked the points, no spark. New condensor, no spark. Checked the spark plug wire to ground and it has continuity. WHAT?? No wonder it won't fire! It's being grounded. FOund a mouse nest around the coil with chew marks on it. I now have a new coil, points, condensor. Checked the new coil...it reads continuity to it's own frame! I thought the spark plug wire should not be grounded. To control the spark is to interrupt power from pints, or to ground that plug wire. But...the plug wires are already pre-grounded. What am I missing?
Model: 243431
Type: 0520-01
Code: 770214
B&S Easy Spin 10HP (circa early 70's...?)
 

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Discussion Starter #3
Unless it's an internal switch. The coil is sitting in my lap. Not connected to anything else. Continuity between the spark plug wire end and the coil frame. Brand new.
 

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There has to be continuity, on your lap or not, as the internal winding OTHER END must be grounded for there to be current flow.
The spark is developed in the secondary winding when the primary winding collapses as the points open. The condenser is just there to catch the 'back EMF' when the points open.
If you look at a schematic or diagram of the engine electricals, you will see the symbol for coil is two spirals parallel to a symbol like a 'bar' between the coils. One end of the output (hi volt) side winding goes to the plug, the other to ground. The other coil is connected such that the magnets cause it to become an electromagnet itself(generate flow) and when the points open, that flow stops. In some, there is a common point of ground between primary and secondary windings shown on the schematic.
tom
 

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Discussion Starter #5
I see. Makes sense, Tom. There's no secondary 'coil' to receive from the primary until the power is built enough to complete the circle to ground. (aka spark !)
Thanks, Tom.
 

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Discussion Starter #6
So, a new coil, condenser and points at .018. Air gap at .02. Still no sprak. It almost kept running but quit after maybe 12 hits. No there's no spark again. It must be something simple I'm missing. I looked for a schematic of the enigne in it's simple form. It's the old style rope start. Cannot find one. Need help on that. No key, no battery, no starter. Wind the rope on the drum five or seven times and pull. used to sput-sput and take off. Now...nothing.
 

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Could you not find an electronic ignition for it?

I had an old 4HP B&S and put an electronic ignition on it and left the points under the flywheel, never even pulled the flywheel ... runs great.
 

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Couple thoughts, what plug are you using? Is it possible it has conduction across the ceramic center? Did you try another plug?
Have you taken a hacksaw blade and checked the magnets on the flywheel? The should try to grab the blade, and will hold it in place if good.
I would bet more on the plug, as losing magnetism takes some doing. Hitting with a hammer can at least partially demagnetize.
Is it possible the magneto(coil) is mounted upside down? I have heard of that causing problems. I think mostly with timing, but I have not checked personally.
If you apply DC to the condenser, + to the wire, and - to the outer, it should take a bit of charge, and hold it for a while. A transistor battery would charge it up, and you could then check using a VOM to see that it is not shorted as it should have V measured from wire to outer case for a short while. It will likely leak off slowly. I remember hearing stories about condensers(capacitors) getting charged... and then being tossed at the new guy... bzzt. If bad, it will ground out any juice that would be normally used to build a magnetic field, and then .. so no sparky.
Check the mechanical connections and insulation. If you do not put the insulators where they were designed to be, the volts will not be generated. The 'ribbon' that goes to the points should be insulated from ground, being connected to ground only when the points close. The pivot will have insulation as will the wire to the condenser. If you miss a tiny little fiber washer, the pivot can get grounded and no more spark.
I have not looked at one for decades, so this is all visualizing, longer ago than I want to know.
tom
 

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I have the 243431 B&S 10 hp engine on my garden tractor. Same vintage.

When I was struggling to get spark, i found the problem was the points. I finally gave up on points and went to an electronic ignition module (NOVA II, about $15). Solved all my problems.

If you want to try to keep the points, make sure they are perfectly aligned when closed. Sometimes even the smallest offset can prevent a spark from occurring.
 

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Yeah, points is really old school on those small engines ... most people throw on the electronic ignition, really cheap usually, and fires right up and certainly less hassle over the long run.
 

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I have had a Clinton/Tecumseh powered Craftsman that I think has points. Have not had to do a thing to them since it was given to me around 1989. Carb has needed fiddling, but nothing sparky wise, even the plug is the same one. The plastics have crystalized and fallen to bits, so it looks rather forlorn showing its ducting and tank, but it mostly starts on the first pull. Well, it did until I moved it out of the garage, and have it sitting outside under an overturned 'storage tub'. I don't think it can get rain to fall upwards, but it is a bit more stubborn waking up.
Thing is, it is over 40 years old, and has never had ANY ignition service. Valves, yes. Sparky, no. Float is a bit finicky, but works in general, and I have a replacement needle/seat in my parts box. It does have new shoes, as the old wheel plastic started turning into chunks. Wheels are not cheap. More $ in them than anything else. But it is easy to roll and trim where a rider is cumbersome.
tom
 

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@tom,

Agreed, ... if it aint broke, don't fix it ....

But on a 50 or 60 year small engine, when the points fail, much easier to not pull the flywheel and mess with points, but just put on electronic ignition ... cheaper and more efficient ...... :)
 

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"Most" Briggs & Strattons can be upgraded to electronic ignition just by replacing the coil with one off a similar HP later engine ,that has the built in pick up unit to detect when the flywheel magnet passed by it ,to fire the plug at the right time..

Some older engines that had 3 legged coils couldn't be swapped for an electronic one,and some also had to have the flywheel magnets re-polarized to work with those aftermarket modules,some just wont work period ..

I have not had much trouble with points,unless I let the engine sit unused for months--then they may get a film of corrosion on the contacts ,that has to be cleaned off in order to get the spark back...that can be a pain when pulling the flywheel off is required..but I have tried several of those Nova II modules and had poor luck with them...engine with points will start with even a slow pull on the rope,while the electronic ignition requires a brisk rapid yank or else no spark will happen..the modules can die suddenly without warning too,two of mine did after only being used a few hours..
 

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I have seen the 'magic smoke' get out of many a product, but it seems that coils and magnetos don't give any signal when they get zapped or decide 'its time'.
Have had engines that ran fine yesterday, put away, take 'em out the next day, and no spark. A Honda, which was surprising to me. Everyone says they are perfect and never break, right?
The CDI systems used in some earlier(1990's) Clinton/Tecumseh outboards would fail with a no-spark condition. Appears a cheaper capacitor was installed that was right at the upper limit of its voltage rating. All bits were 'potted', so it took some ingenuity to figure the solution. Given replacement parts are NLA, it is good to know my old Eska outboard can be repaired if/when it decides it doesn't want to run any more.
In general, that would not be a problem with a points style ignition. Kind of a PITA for something like that to fail when out in the middle of the lake, or floating down the river. They were not the only brand to have spark failures with the 'new and improved' electronic ignition systems. Mercury at the time seemingly had a run of poor systems.
tom
 

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Not sure if yours is the same as mine but I just worked on my B&S 12 hp circa 1968 and the resistance from the spark plug wire to the coil frame should be around 2.5k to 4K ohms. You might need to set your meter to a lower range to see that. I had no spark but mine was measuring open. New Stens replacement worked like a charm.


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Discussion Starter #17
The spark plug wire is the large one. Obvious to me. The wire on the right side with the eyelet I know for sure goes to the coil mounting screw. But....what does the snipped wire on the left side go?
Driving me crazy! Cannot find a schematic in any of my Briggs books.
Thanks for ANY help!
 

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That wire is the kill wire. Goes to ground to stop the engine.


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Discussion Starter #19
Okay, Smalljob. I'll set it all back up with that wire not in contact with any ground. Hopefully that's the answer. You see, that wire went to a terminal on the rear plate of the engine shroud. That terminal has a wire on the outside that then went to two things....one was the points/condenser, but the other wire went to a ring terminal that was attached to a small square of steel and was attached under one of the points cover can screws. Effectively ground it. It was always like that, and it ran just fine. I will try it as you suugest and hope for a running engine on Friday! Thanks for the help.
 

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Just make sure you have a way to stop the engine. You can ground the tip of the spark plug depending on the type of connector. OR always pull the spark plug wire " carefully"
 
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