250 Death Coil

[Sam R]

So I got a treat this week: a customer brought in a 250 with a broken pull rope.

Finding most everything to be in order, I'm only suspicious of the carburetor as it has some hallmarks of tampering.
Turns out the step I skipped because of a busted rope would have revealed the true fault with the saw.

Once I'd reassembled the machine I put a new rope in it, cleaned up the carburetor, replaced the fuel filter & plug just to rule out those as issues.

The 250 would pop every 3rd or 4th pull. I finally gave up and decided there were internal problems with the carb. So I swapped it out (I figured a safe bet since this was a rebuilt B revision of a carb that's now on E).
Same issue. So I look back at my notes - I never did a spark test! I put the spark tester on it and find that Lo and behold there's no spark coming out every 2nd or 3rd pull. Ruled out the short circuit wire and determined the saw to have a bad coil.

I've been at this awhile and this is the first time I've ever seen a dead coil on a machine. I was under the impression they worked or didn't but I guess sometimes they'll be intermittent like that. It never started long enough to heat up. I love my job.

 

[grizz55chev]

Looking back at some old posts, seems you need to gap the coil a little tighter on the 250 or you get no spark. Try gaping it with a folded piece of paper instead of the usual business card gap. Worth a shot.

 

[Sam R]

I checked that, I used Stihl's gapper too, which is just a metal version of same. When the new coil comes in I'll try gap it the same and if same issue I'll look at a tighter gap.

 

[cus_deluxe]

Death coil, sounds like a badass name for a metal band, lol.

 

[SteveSr]

I have seen dead/intermittent Stihl (Walbro) coils. All of these have been on 4137 series (FS-80) weedeaters.

 

[Colt Marlington]

Death coil, sounds like a badass name for a metal band, lol.

Or a boa constrictor.