Good Day all; New to the site and hoping that someone out there can answer my question.
I have a chipper/shredder powered by a Briggs model 120000 series engine which is giving me fits. It worked great earlier this year but now won't start. Checked the starter, it's bad. Checked the solenoid, it's bad too. Dismantled all the wiring associated with the starter and tried to start the engine but no go. I tested the spark generator (resistance only) and it seems ok, and re-gapped it to specs (it was very narrow). The spark plug test was equivocal so I replaced the plug (the new one tests about the same as the old one - wild fluctuations in resistance between top and body). After putting it all back together, there is no spark when I pull the manual starter rope.
In desperation, I turned the engine with my 3/8 drill, using a socket on the flywheel bolt. At low rpm there is no spark but when I rev it up a little there is a spark. Not what I would call a nice big fat spark but I think it would be plenty to run the engine. I didn't try that because I don't like the idea of running an engine with the flywheel etc exposed.
The question is, is this an indication that the generator is going bad?

 

You've definitely got something wrong. If you disconnect the spark plug wire from the plug and hold it in your hand and then manually turn the flywheel magnets past the magneto with your other hand, you should get a pretty good jolt.

Your magneto coils could be bad (for instance, insulation punched through by cranking the engine with the plug wire disconnected so that there is no where for the spark to go except through the insulation within the magneto itself.

I don't know about that particular model (there isn't even enough information to determine if it is a vertical or horizontal engine), but underneath the flywheel there is likely a set of points and condenser that might need to be replaced (though these typically last the life of the engine).

 

Points haven't been used for over ~50-years.

There can be only 2 problems ............

The Ignition-Coil has become "loose" and is spaced too far away from the Flywheel,
OR,
The Ignition-Coil is bad.

Most likely, the Ignition-Coil is bad, replace it with a new one,
and then carefully adjust the gap between the Ignition-Coil-Armature, and the Flywheel.

Done.
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.
.

 

Points haven't been used for over ~50-years.

Tell that to the engines on my lawnmower and snow blowers, all of which are significantly less than fifty years old.

 

and then carefully adjust the gap between the Ignition-Coil-Armature, and the Flywheel.

Put a business card (or something about the same thickness) between the coil and the flywheel with magnets next to the coil. Loosen the coil mountings and the magnets will pull the coil tight to the card then tighten to coil mountings. Now rotate the flywheel and remove the card. Rotate the flywheel to make sure the coil does not touch the flywheel.

 

Good Day all; New to the site and hoping that someone out there can answer my question.
I have a chipper/shredder powered by a Briggs model 120000 series engine which is giving me fits. It worked great earlier this year but now won't start. Checked the starter, it's bad. Checked the solenoid, it's bad too. Dismantled all the wiring associated with the starter and tried to start the engine but no go. I tested the spark generator (resistance only) and it seems ok, and re-gapped it to specs (it was very narrow). The spark plug test was equivocal so I replaced the plug (the new one tests about the same as the old one - wild fluctuations in resistance between top and body). After putting it all back together, there is no spark when I pull the manual starter rope.
In desperation, I turned the engine with my 3/8 drill, using a socket on the flywheel bolt. At low rpm there is no spark but when I rev it up a little there is a spark. Not what I would call a nice big fat spark but I think it would be plenty to run the engine. I didn't try that because I don't like the idea of running an engine with the flywheel etc exposed.
The question is, is this an indication that the generator is going bad?

Make sure the points are clean and bright. You could clean them with a fine file or fine emery paper but don't go overboard on this.

 

Make sure the points are clean and bright. You could clean them with a fine file or fine emery paper but don't go overboard on this.

Thanks Albert, but there are no points

 

You've definitely got something wrong. If you disconnect the spark plug wire from the plug and hold it in your hand and then manually turn the flywheel magnets past the magneto with your other hand, you should get a pretty good jolt.

Your magneto coils could be bad (for instance, insulation punched through by cranking the engine with the plug wire disconnected so that there is no where for the spark to go except through the insulation within the magneto itself.

I don't know about that particular model (there isn't even enough information to determine if it is a vertical or horizontal engine), but underneath the flywheel there is likely a set of points and condenser that might need to be replaced (though these typically last the life of the engine).

According to the parts manual, there are no points. There has been no reason to rotate the engine without a plug, either in the head, or grounded against the head to check spark.

 

Points haven't been used for over ~50-years.

There can be only 2 problems ............

The Ignition-Coil has become "loose" and is spaced too far away from the Flywheel,
OR,
The Ignition-Coil is bad.

Most likely, the Ignition-Coil is bad, replace it with a new one,
and then carefully adjust the gap between the Ignition-Coil-Armature, and the Flywheel.

Done.
.
.
.

Thank you. My assumption is that the coil is probably going bad but I haven't seen a case where I get a spark at high rpm and not at low rpm. I gapped the coil back to specs with a feeler gauge after finding it was really narrow but did not try it at the original setting.

 

The Internal-Circuitry includes a Capacitor,
quite often a Capacitor's specifications will degrade
with age, or usage, or accidentally exceeding it's maximum-capabilities.

Comparatively speaking, most other common types of Electronic-Components
virtually never degrade in performance when operated comfortably within their specifications.
.
.
.

 

The Internal-Circuitry includes a Capacitor,
quite often a Capacitor's specifications will degrade
with age, or usage, or accidentally exceeding it's maximum-capabilities.

Comparatively speaking, most other common types of Electronic-Components
virtually never degrade in performance when operated comfortably within their specifications.
.
.
.

Do you mean the internal circuitry of the coil/spark generator? Or is it hidden in some other component?

 

There can be only 2 problems ............

Do not forget bad multimeter, probes or else; operator error...

 

Do you mean the internal circuitry of the coil/spark generator? Or is it hidden in some other component?

.
There are no "other" Components,
every part is sealed in high-temperature-Plastic,
right along with the wound-Coils,
as a single-sealed-unit.

The only test recommended by the factory manual is whether or not the Coil can generate a
Spark of a specific length at cranking RPMs.
Briggs & Straton even sells a "Spark-Tester-Tool" with a preset minimum-Test-Gap built-in.

This is a "Go/No-Go" test.
Ether the Coil passes, or it requires replacement.
There are no other "tests".
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