Briggs and Stratton 123K02 No Spark

itsgalf · Aug 11, 2018

Hello all,

I had purchased an Briggs and Stratton lawnmower that some guy couldn't start for $40. Assumed it would be an easy enough fix.

Model: 917.378451
Engine: 123K02-0183-E1

I got a kit to rebuild the carb and then replaced the spark plug. Figured that should get it going.

But there seems to still be no spark. I followed some video and checked the resistance on the ignition coil. The old ignition coil showed 'OL' so pretty sure that was no good. I ordered a new one on amazon from HIFROM that looked to have same part number. The new one looked a little different than the old one, but it fit the mounting bolts so I installed that.

Saw this on the HIFROM amazon page
"4. Please note that: the one we sell is for later 802574, not for the earlier, please check the pictures carefully before you buy it."

Anyways, I tried to start again and still didn't work. No spark still. I disconnected the wiring going to the kill switch and tried to test for spark again, but nothing. The magnetron is spaced at 0.010"

Now a few questions:

1. The flywheel has the two raised areas on opposite ends that wipe past the ignition coil. Are both ends supposed to attract metal? Only one side will pull in metal, the other side does not.

2. Is the only possible problem here the ignition coil, flywheel magnet, or spark plug? That's what I'm figuring, but the ignition coil and spark plug are new.

3. Is the new ignition coil not being the same as the old one the problem? The coil itself seems fine and has a good resistance reading across the coil (dunno, just saw some video saying it should read X Ohms across).

Thanks
- Marco

Here's a picture of the old and new ignitions coils side by side with each other

Briggs and Stratton mower ignition coil.jpg

itsgalf · Aug 11, 2018

So I followed some advice on another forum to change the coil out with a 'known good'. I should have done that originally, just wasn't thinking.

I had another Craftsman mower w/ B&S Engine that was quite similar. Took the ignition coil from that and used it on the inoperable one. Started right up. *face palm*. Looks like that Chinese coil is NFG

shiftsuper175607 · Aug 11, 2018

itsgalf said:
Hello all,

I had purchased an Briggs and Stratton lawnmower that some guy couldn't start for $40. Assumed it would be an easy enough fix.

Model: 917.378451
Engine: 123K02-0183-E1

I got a kit to rebuild the carb and then replaced the spark plug. Figured that should get it going.

But there seems to still be no spark. I followed some video and checked the resistance on the ignition coil. The old ignition coil showed 'OL' so pretty sure that was no good. I ordered a new one on amazon from HIFROM that looked to have same part number. The new one looked a little different than the old one, but it fit the mounting bolts so I installed that.

Saw this on the HIFROM amazon page
"4. Please note that: the one we sell is for later 802574, not for the earlier, please check the pictures carefully before you buy it."

Anyways, I tried to start again and still didn't work. No spark still. I disconnected the wiring going to the kill switch and tried to test for spark again, but nothing. The magnetron is spaced at 0.010"

Now a few questions:

1. The flywheel has the two raised areas on opposite ends that wipe past the ignition coil. Are both ends supposed to attract metal? Only one side will pull in metal, the other side does not.

2. Is the only possible problem here the ignition coil, flywheel magnet, or spark plug? That's what I'm figuring, but the ignition coil and spark plug are new.

3. Is the new ignition coil not being the same as the old one the problem? The coil itself seems fine and has a good resistance reading across the coil (dunno, just saw some video saying it should read X Ohms across).

Thanks
- Marco

Here's a picture of the old and new ignitions coils side by side with each other
View attachment 39713

The mower has a bail cable correct?
You pull a handle before you try and start it.
That cable goes to the engine.
Underneath the cover there is a kill switch that grounds the coil. A wire you removed from coil.

That bail cable must open the kill switch.
It can be broken
The kill switch can need adjusting (bending a little) so as it is open when the handle is pulled.

itsgalf · Aug 11, 2018

Hello shiftsuper,

I found out that it was the new ignition coil that I bought isn't working. I used the coil off of my other Briggs and Stratton mower and this mower starts up now.
Thanks for the reply

bertsmobile1 · Aug 11, 2018

itsgalf said:
Hello shiftsuper,

I found out that it was the new ignition coil that I bought isn't working. I used the coil off of my other Briggs and Stratton mower and this mower starts up now.
Thanks for the reply

Inside the coil is a micro chip which closes to path to ground ( just the same way points used to ) to fire the coil.
Remove that wire and the coil should fire but you will not be able to turn the mower off.
That is the way to check it, if it does not work with the wire off it is toast.
Some cheaper multimeters can fry that chip when doing a resistance reading.

The flywheel has to be balanced so a weight equal to that of the magnets has to be placed opposite the magnets or it will vibrate worse that something you might buy from an "adult entertainment " shop,

AS for stuff bought on line
1) factorys in China never scrap anything so when Briggs reject a batch as being substandard- faulty they get sold to some one else & end up on line.
2) OEM means the factory that makes them for Briggs made that coil but does not meant it was good enough fro Briggs to buy it
3) fits means it will go into the same space, it does not mean it will work

If you believe what internet vendors tell you, there is now a module that will fit every Briggs mower engine under 7 Hp when in fact there are 5 of them.
If in doubt go to the web catalogue of a real after market supplier like Rotary, Stens, Oregon, Prime Line.
Search your engine number, then search Briggs Coil.
If they list more than one part number then the coils are different.

And despite Chinese coils being a lot cheaper, most of the afore mentioned companies sell coils from Mexico, Brazil or Italy

itsgalf · Aug 11, 2018

Hello bertsmobile,

I don't have any experience with points and condenser system. I've read about it though.
Anyway another guy had suggested I install the coil upside down just in case the coil electronics was assembled incorrectly in China. Seemed strange, but tried it anyway - didn't work.

Remove that wire and the coil should fire but you will not be able to turn the mower off.
That is the way to check it, if it does not work with the wire off it is toast.

I was trying the spark test with the kill wire unplugged. Is that what you meant?

Thanks for the good info about buying parts online. Nice to know

bertsmobile1 · Aug 12, 2018

Yes ,
Kill wire unplugged.

Hall effect triggers are polarity sensitive so flipping it over changes the polarity of the induced current.

Briggs and Stratton 123K02 No Spark

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