Stihl ms181c no spark

[Hugh82]

Hi guys,
I have a Stihl ms181c that died one day. It lost compression. I took off the exhaust to find the piston scored and piston rings out of shape, but not stuck to the piston. I put it down to using old petrol.

Since it was during the lockdown I decided to change the cylinder and piston myself. All is good in that department, plenty of compression etc.

But the new problem is that I have no spark. I have changed the plug, and also the ignition coil. I have isolated it from the throttle but still nothing.

Attached is a picture of the ignition system. I am questioning the part labelled 'no.9', it's a torsion spring. I dont have it, as far as I can see. I was at a dead end, so looked up the ignition system diagram to see if I had everything.

Is there anyone familiar with this saw that might be able to help? I have the correct distance between the flywheel and coil too.

 

[trains]

That looks like the coil that goes inside the spark plug boot, to provide spark from the plug wire from coil, the little hook you see digs into the wire past the insulation and into the core, the round bits fit over the end of the spark plug, look inside the plug boot, should be there.
Not hard to remove plug boot, and have that come out if your a bit rough.

edited to add, use a business card between the flywheel and coil, or fold over some paper twice and use that, turn flywheel after, to ensure its not out of round/ etc and clears it when it rotates.

 

[Hugh82]

Hi trains, thanks for your input. I was thinking the same. I'm a newbie at this. And was hoping that I didn't lose anything. Anyway, the spring is in both the new and old plug boot.

Regarding the distance from the flywheel to the coil, I admit I threw it back together and tried to start it 5 or 10 times, not realising I needed a gap. My bad, but I have it set with a business card now. Still nothing with both coils. Magnetic screwdriver is attracting equally to both magnets on the flywheel.

Any other ideas? Might I have damaged the flywheel from not initially creating a gap? No visible marking on the flywheel.

It's either something big or something stupid, but it's got me. Any help greatly appreciated.

 

[trains]

Did you refit the new spark plug boot, and spring coil into the coil wire correctly ?
best to push thru coil wire (from magneto) thru plug boot, then fit the coil that goes onto the spark plug, with the pointed barb into the coil wire, then draw the boot back over it whilst keeping the wire barb in the coil wire.
Should have spark.
Only guessing and assuming that somehow thats not connected.