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Stihl BR550 no spark

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2017/12/07 15:07:20 (permalink)

Stihl BR550 no spark

Have a BR550 that has intermitent no spark. Sypmtoms have been. 
Dies when blowing leaves. Starts right back up on one pull. Didnt die until it got hot, about 20 minutes. 
Now it wont start. 
I removed flame arrester from muffler. Replaced fuel filter in tank, and primer bulb as it had a hair line crack in it. Had to remove carb partially from cylinder to do so. 
I have tested the kill circuit with a meter by disconnecting blue and black wire from coil. It tests correctly on Ohm meter when kill switch is turned on and off. 
Cleaned magnets on pully to ensure not the issue. 
Replaced the spark plug. Removed it, attached to ignition wire and grounded plug. With lights off in my garage I saw no spark. 
Repeated process several times and got spark only once. Also hooked meter to two spades on coil with leads to kill switch off. 
Shows voltage when I pull starter cord. 
Has anyone had similar success fixing above? My experience is a coil dies or gives spark. I dont want to throw parts at this but am leaning toward a coil? 
Any input would be appreciated. 

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    Re: Stihl BR550 no spark 2017/12/16 19:21:28 (permalink)
    Actually more common than you think for the coil to work for 20-30 minutes then fail. Cool off and then work again till it get hots.
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    Re: Stihl BR550 no spark 2018/05/06 09:15:04 (permalink)
    The reason for working on leaf blower is that it quit running about 2 months ago, and when I tried to restart it, I could feel that it had no compression. I first checked the valve clearances, which were good so I figured there is a hole in the piston or a broken valve.
    I was taking the fan off so I could get the engine off. When I was trying to get the nut off, I was holding the fan not knowing that it was attached to the fan. I was using penetrating oil and trying over and over to get the fan off. Then I found that I had a metric tap that would work as a piston stop, the fan/nut came right off. But I feel that repeatedly trying to get it off with the impact gun must have damaged the flywheel internally.
    When I got the engine apart, what I found was a lot of carbon build up around the exhaust valve, port and on top of the piston. I cleaned everything up and put it back together, has compression now but no spark.
    Waiting for flywheel to show up and then will post results. Hopefully will arrive this week.
    post edited by cowolter - 2018/05/06 09:17:25
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