Coil failure seems to be common in 391's. They have an electronic rev-limiter in the coil which is activated (earths the spark) at or above a pre-determined rpm. This is the black wire that connects to the coil assy via the spade terminal. It is normally open (high resisitance) and shorts the spark ,when required, to limit the revs. The other wire is a simple switch that shorts the coil when you flip the lever all the way up. Coil failure is caused by the rev limiter short-circuiting (low resistance) permanently. Easy to replace and low cost. BTW the magneto-flywheel gap is 10 thou (0.010")
At the mark of 17:50 you may say you talk to yourself, but honestly, I never saw people pointing things to themself!!! Lol! You might like to have a spark plug cleaner, using special grit and compressed air. Old and fooled spark plugs come out brand new. And it cleans the ceramic insulation near the spark probe, reducing lost of electricity. I've got 2 main saw. My MS250 doing 90% of the logging work in the forest. When it comes to bucking, I use mainly the 026. I am fine with smaller saws, I barely have trees over 16 inches in diameter. Thanks!
@@timberterra I do that often! Only to find while editing I was talking for a straight 5 minutes... People don't want to hear it, they want to see it! Have a nice weekend!
Morning from the UK, a good informative video, and good to see you solved the problem well done that man. Thanks
Nice job Glenn, good that you can do your own repair, smart man.
Coil failure seems to be common in 391's. They have an electronic rev-limiter in the coil which is activated (earths the spark) at or above a pre-determined rpm. This is the black wire that connects to the coil assy via the spade terminal. It is normally open (high resisitance) and shorts the spark ,when required, to limit the revs. The other wire is a simple switch that shorts the coil when you flip the lever all the way up.
Coil failure is caused by the rev limiter short-circuiting (low resistance) permanently. Easy to replace and low cost. BTW the magneto-flywheel gap is 10 thou (0.010")
Thanks. Appreciate the additional info!
At the mark of 17:50 you may say you talk to yourself, but honestly, I never saw people pointing things to themself!!! Lol! You might like to have a spark plug cleaner, using special grit and compressed air. Old and fooled spark plugs come out brand new. And it cleans the ceramic insulation near the spark probe, reducing lost of electricity. I've got 2 main saw. My MS250 doing 90% of the logging work in the forest. When it comes to bucking, I use mainly the 026. I am fine with smaller saws, I barely have trees over 16 inches in diameter. Thanks!
I think I might have been explaining something, but in the end, didn't think it was worth including. Haha.
@@timberterra I do that often! Only to find while editing I was talking for a straight 5 minutes... People don't want to hear it, they want to see it! Have a nice weekend!