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No spark to mower engine

daveallen's Avatar
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10-21-01, 05:01 PM   #1  
My craftsman riding mower quit today. I am getting no spark to the plugs. I think the problem is in the magnito. Does anyone know how to test to see if the mag is working? Also what is the clearance between the mag and the flywheel?

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Fisher's Avatar
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10-22-01, 02:00 AM   #2  

Post your engine's model numbers so we know what
you have, but if it is fairly new, it won't have
points. There is a small wire plugged into the magneto
[coil], unplug it, then recheck for spark. If you have
spark, then one of your safety switches or wiring
may be at fault. Have you replaced anything electrical
or done anything to it lately?

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10-22-01, 03:08 AM   #3  
The engine # is 461707, it is a 20.5 HP Briggs. I did have a problemwith the mag. One of the bolts that holds the mag to the case came lose and the engine quit. I took it apart and found that the tab on the case had broken off. I taped for a longer bolt and put the mag back on. Now i don't get any spark. I have been running with all of the safty switched disabled for some time now.

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10-22-01, 05:35 AM   #4  
If your repair did not alter the height or position
of the coil, then if the coil doesn't spark then the
coil is bad, fancy equipment is nice, but if the
coil does not fire with the kill wire disconnected,
then it is bad. The reason I asked is that if you
had a wiring problem or wrong switch installed and
it sent 12 volts to the kill wire, it would damage
the coil. There is a remote chance that a shock
to the flywheel affected it's magnets, but it is an
occurrance I have yet to see.

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10-23-01, 03:25 AM   #5  
How about this? When i taped the hole to mount the mag i used a quarter inch bolt. I had to drill out the mounting slot in the mag to excrpt the larger bolt. Could this have effected it in any way?

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10-23-01, 02:59 PM   #6  
Clarification Requested

Hi: daveallen

First point:
I am not sure which tab on what case broke off. Would you clearify that point.

Second point:
If the tab that broke off was the one on the magneto, replace it.

Third point:
When the magneto "came loose" exactly what happened?
Did it get damaged? Damaged the flywheel? The flywheel magnets?

Fourth Point:
I have never heard of this happening before. Not saying it couldn't just never heard of it. Unless the magneto had been removed or adjusted prior and was not secured correctly.

The air gap distance should be about .016 which is about a sheet of computer printing paper folded over once. Or a thin business card or card from a deck of playing cards.

Regards and Good Luck.
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