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Discussion Starter · #1 ·
Hello all,
I've got a recently purchased LT12 that ran great last week but now has no spark. I've removed the steering head assembly and driveshaft from the motor which is a twin cylinder briggs 12.5 HP. Before I remove the engine cover and tear into this, is there specific things to look for and do.
My small engine experience goes back to points and condenser not electronic ignition as this has. Does the module/Coil need to be replaced? If so is there a testing procedure.
 

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No spark?

The magnetron ignition is pretty simple. Make sure there is about a business card of space between the flywheel magnet and the magneto. Off that will be the spark plug wire and also a grounding wire to kill the engine.

Really, I'd think it more likely that the kill wire is grounded by a broken (or working) safety switch than broken ignition. But you could test that easily just by disconnecting that kill wire.
 

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Discussion Starter · #5 ·
There is no coil?
This is a horizontal twin cylinder engine.
Where does the kill wire run from.
There is one small wire bolted to the head.
On the other side is another with a plastic connector that separates.
Is there anything under the flywheel to replace or adjust?
 

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No.

Ok.

It runs from the magneto through the wiring harness. If anything grounds it there is no spark. Things that ground it are the ignition switch and most safety switches.

I dont know what the small wire bolted to the head is.

I don't know what the plastic connector is. It could be the alternator circuit, it could be the kill circuit.

No, assuming it's relatively new (1980's IIRC) the magnetron ignition is a modular piece outside the flywheel. Timing is adjusted by the magnet's position on the flywheel, which is held in place by the flywheel key. But the timing being off would still allow it to spark. Take the engine cover off and take some pics.
 

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i got one of those myself, and it runs like a champ. changed ignition switch and checked gear lube on drive system. if i were you, i would replace the entire igniton system. i found it to be very beneficial on the lt 11 i had and the lt 12 i currently have. you might also wanna check the rear end and put some gear lube in it if needed. should just be a black plastic cap on top of the trans op the top left side of the case. the rear tires can some times be a pain in the a** to locate. other than that, its an excellent machine.
 

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Discussion Starter · #8 ·
i got one of those myself, and it runs like a champ. changed ignition switch and checked gear lube on drive system. if i were you, i would replace the entire igniton system. i found it to be very beneficial on the lt 11 i had and the lt 12 i currently have. you might also wanna check the rear end and put some gear lube in it if needed. should just be a black plastic cap on top of the trans op the top left side of the case. the rear tires can some times be a pain in the a** to locate. other than that, its an excellent machine.
When you say replace the entire ignition system, can you specify all the parts you would replace.
 

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switch, solenoid, magneto, and it wouldnt hurt to throw a fresh spark plug in it. i just had to put a new switch in mine and i was good to go. you might also want to try sanding off the flywheel with a piece of sandpaper and re-setting the magneto. there should be a matchbook thickness between the magneto and the flywheel.
 
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