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Darn B&S Ignition

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I drag out my 3415H Sovereign to get ready to sell, it had not been run for several years.   I hooked up a battery and turned it over, and heard lot of stuff rolling around in the blower housing.   So I removed the engine took off the blower housing and found lots of junk from the mice, cleaned it up and found I did not have spark.  Cleaned the coil and flywheel, still no spark, installed another set of points and Voila great spark.  

Started and stopped the engine several times on the bench, then put it back into the tractor, drove the tractor around a bit and it died and NO Spark!

I fiddled with points and condensers - No spark.  Installed a NOVA II that I had and still no spark.   

After playing with these tractors for almost 50 years, I still shake my head on the Briggs magneto ignition system.  Many times, out of nowhere these Briggs engines will lose spark, clean points and gap, that didn't work.  Install new points and condenser, that didn't work.  Get desperate and try an old set ... and you get spark sm00.   It can drive you nuts (maybe you have to be nuts to collect these tractors in the first place).

Looking into the Briggs manual there is no information on ohm checks for the wires/leads coming out from behind the tin.  Does anybody have an info, so I can determine if I have a bad magneto?

I do not want to pull that engine out again...I think I will go to a battery external coil.  I am sure that a Kohler coil with internal resistor will work, but what other coils will work?   Does it need to be 1.5 ohm, or 3 ohm, or what?

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Rule of thumb that I was taught in regards to external coils is 

6 volt = 1.5 ohms

12 volt = 3 ohms or 1.5 ohms with external resistor

For my Kohlers I run coils with 3 ohms.

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Thank you.  I’ll be at fleet farm this morning, I’ll pick up coil there.   Last night I tried a coil from a Kohler and it started instantly.  And I like how you can idle the engine down, and it keeps running with the battery ignition.

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