Rebuilt Stihl MS-391 not getting spark

[HarleyT]

The newer style coils put out a very weak spark, and cause many goose chases.

 

[farmhard]

I had a post about a TS800 making me mental.
What I found is to use a SPARK GAP tester and not a test light or LED. It would light up and LED but not jump a gap. Also check your P/N on the flywheels before swapping and match to the coil #.
Those wires to the kill switch like to rub and short out against each other and to ground.

 

[farmhard]

Also, I'm probably going to get $hit on here but my 391 has a Timesert in the spark plug thread -NOT A HELICOIL and I have no problems with it. Helicoils don't last. We use Timeserts often over purchasing new barrels. Obviously budget and wear are considerations.