MS261 No Spark Mystery

Mile Green

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Hi. Jul.12.2022

I have a Stihl MS261 that I've owned since 2011 - not heavy use, I've cut about 75 cords with it, always in dry summer months. Saw visually appears to be in top condition. There is no heating feature on this saw.

Last summer I could not start it so I installed a new Stihl module ($150 !!!) and spark plug . It worked fine for a couple of months. I then put the saw away for several months with fuel stabilizer run through it. As per a Stihl tech, I left the fuel in the carb. (Yes I know, the manual says to drain the fuel - not sure which is correct.)

Now, once again, it won't start after working fine about a year ago. I pulled the spark plug and noticed it was fairly dry. I stuck a finger in the spark plug hole and pulled the cord - my finger was slightly moist. Compression seems fine.

Then I checked for spark - there is NO spark. I checked the shutoff switch ground circuit, and it appears to be working fine. To be sure, I disconnected the wire going to the tab on the ignition module just to ensure that the primary winding was not shorting out to ground. Still NO spark. The spark plug gap is .025".

I checked the magnets on the flywheel - no discolorization. Fairly strong pull on the "N" magnet to my screwdriver. I tried a different spark plug to no avail. The ignition module bolts are tight and the flywheel gap is .007 (.178mm).


The resistance from the spark plug boot to the ignition module ground is 2 Kohms as per spec.

Now I haven't a clue as to what to do. How could the ignition module go bad after sitting for a year????

Any thoughts or advice would be greatly appreciated.

Thanks in advance for any input,
M...
 

Oakie

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Is your crank bearing ok, the shaft is not moving about.
Is the coil earthed to the crank case, clean connection there.
Is there a key in the flywheel is it ok, the wheel has not moved.
 
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