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Magneto issues

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Norman52
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2018/10/04 16:24:22 (permalink)
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Magneto issues

I have an Intek 8.5 Horizontal 121237 0135 B1 that just died. I checked for spark, no spark I replaced the magneto 796964 and it started first pull and ran 10-12 minutes and dies, no spark. Checked using my spark tester, nothing, check by grabbing the lead, nothing. Let it sit over night and it started first thing and ran 10-13 minutes and died again, It wont start the rest of the day. Next day I plugged my spark tester inline and it showed spark like crazy and the motor fired right up. I turned it off and removed the tester and fired it up again and it ran 10-12 minutes and dies. Shot some starting fluid in it just to make sure it wasn't fuel and not even one pop. Checked to make sure the magneto was installed correctly and the small ground wire is on the bottom and the arrows are pointed correctly. Oil is full, it doesn't seem hot. When I changed the magneto I blew all the grass clippings and stuff around it  so it is clean and getting air. New Air filter. It starts on half a pull, It has electric start but I never use it as it starts so easy on a pull. Any ideas what to change next?

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    Roy
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    Re: Magneto issues 2018/10/04 21:38:00 (permalink)
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    Is the armature OEM or aftermarket? You could have received a bad one which is not common if a Briggs part. Did you try a new spark plug?
    Norman52
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    Re: Magneto issues 2018/10/04 21:42:49 (permalink)
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    Factory Briggs replacement part and new sparkplug.
    Norman52
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    Re: Magneto issues 2018/10/09 10:26:56 (permalink)
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    . It started right up as usual and died in 11 minutes. No spark and not even a pop on starting fluid.

    So I ordered one more magneto. Again Briggs factory part. I will buff the mounting surfaces to make sure I have a good contact. I will blow out all nooks and crannies to make sure it is getting lots of air cooling. I will trace the small black grounding wire to make sure it isnt rubbing against anything. We shall see....
    Norman52
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    Re: Magneto issues 2018/10/11 17:23:46 (permalink)
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    It started right up again on one pull. ran great for 9 minutes and died. Put it in the shop and tried to start it using the electric starter. It spun like crazy but no spark. i even grabbed the high tension lead and not even a tingle. Took everything apart, installed another new magneto, made sure everything was clean and put it back together. Started on half a pull, ran for 7 minutes, started to die then cleared up and ran for 2 more and died, no spark. Shot some starting fluid in the carb just to see what would happen and nothing. not even a pop.
    Anyone have any ideas or should I just go buy a replacement? I already have $80 in Magnetos that look to be a waste of money.
    AVB
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    Re: Magneto issues 2018/10/11 17:55:40 (permalink)
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    Since it sounds like you have an 12v electric starter setup plus the recoil I am thinking you have a positive voltage feed back on the coil's kill wire. I have seen a couple last year where the ignition switch had a partial short sending 3-4 + volts to coil causing lost of spark.
     
    Try this get one of coil that still starts and run for while. Install it but this time leave the kill wire off the coil and see if it runs without dying. You may need to either choke or pull plug wire to kill later but will let you if it is the coil that is root cause or electrical feedback otherwise.
    Norman52
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    Re: Magneto issues 2018/10/11 18:58:57 (permalink)
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    I just learned something. Since it is part of a lawnVac system it runs at full throttle. 9 minutes now it dies and no spark. If I let it sit for 30 minutes it starts right up and I learned if I leave it at 3/4 throttle it seems to run just fine. I can run it at 3/4 throttle for 60 minutes and it works fine but just crack it to full throttle and it will stop in 1 or 2 minutes and no spark. I thought maybe it is fuel but then it starts cold and runs full throttle for 9 minutes and doesn't spit or sputter. When it dies it just dies. Like you turned it off.
    I will disconect the battery and see what happenes. I never use the electric start as it starts always on one pull.
    I will post the results
    post edited by Norman52 - 2018/10/11 19:44:34
    AVB
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    Re: Magneto issues 2018/10/11 19:31:39 (permalink)
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    Just disconnecting the battery will not work for what I am thinking as the still a charge coming from the alternator (stator). This why I am suggesting disconnecting the wire at the coil and testing.
    post edited by AVB - 2018/10/11 19:56:30
    Norman52
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    Re: Magneto issues 2018/10/11 19:45:03 (permalink)
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    I will try it and let you know
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