Stihl 08s is killing me!

[popopboat]

Hello everyone,
few days ago i started working on a neighbours Stihl 08, hasnt been run for 15 years or so.
Firstly i replaced carb diaphragms, fuel and breather hose, oil seals and cleaned it from inside out.

It took only 5 pulls to start, and after idling for 3 seconds it shut itself off (like kill switch), then i pulled again and it only coughed few times...
Then i recalibrated ignition (breaker point system), pulled and pulled - only few coughs again... Left it as it is, and tomorrow it started flawlessly and actually RAN, so it fixed itself over night, right....
Anyway, after it started always flawlessly, BUT really stuttered when accelerated, exactly like spark is dissapearing or kill switch is engaging (but it had no switch, only open wire).
Recalibrated ignition, cleaned carb few times, no improvement at all.

Then i replaced sparkplug wire, condenser, and breaker point thing(yea) and it wouldnt start, so again i recalibrated ignition timing * few times and then just like that it started and began working flawlessly, acceleration was smooth, no cuts or stutters at all.
Then from all joy and happines i went for a few cuts, and bastard worked again flawlessly for literally 3 cuts, and on 4th cut it started to stutter again! But this time its less like spark problem and it gets worse as the saw heats up (but a serious air leak feels way different than this)

I spent too much time on this shiet, i literally dont know what else to do.
This is the first saw that im loosing my mind on.
Ive recalibrated ignition and recleaned the carb atleast 7 times!

Ive set the ignition as manual says (2.4mm before TDC, 0.4 breaker gap and 0.5mm sparkplug gap)
Carburetor is set on 1 turn out on both L and H, but it doest not really make a difference if i change it.

Heres a video

Sorry for probably a hard to read post.

EDIT: I know on this video it really seems like a carb problem, but sometimes its like that and sometimes it really feels that killswitch is engaging (which is not)

 

[Woodslasher]

Sounds like it's bogging to me. Just throwing out random stuff, is your muffler/spark screen clear and have you tried replacing the spark plug?

 

[popopboat]

Yep, its clean and no spark screen on this old chap.
Replaced sparkplug, no luck.
Carburetor is not clogged and is really clean from inside, check valve works too.

 

[Woodslasher]

Hmm, maybe throw an in-line spark tester on it and see if it is actually losing spark or if it's something else.

 

[popopboat]

Ive tried spinning it with a drill, and it had spark whole time.
Worst thing is that it "broke" and fixed itself 2 times...

 

[Woodslasher]

Ive tried spinning it with a drill, and it had spark whole time.
Worst thing is that it "broke" and fixed itself 2 times...

Having spark and having consistent spark is different. I was suggesting you put the tester on the saw, then fire up the saw and rev it a few times so while it is bogging you can see if it is losing spark or not. Or, pressure and vacuum test it and see if it has an air leak.

 

[Wonkydonkey]

Didn’t some of those old stihl saws have problems with coils going bad or was it the other part of the ignition when it got hot,
Ie runs ok when cold and pisses-about when hot. I know spark plugs can do this, but you’ve changed the plug. And also going from my old motorcycle days, I had a duff s-plug out of the box. So my advice is use a known good plug from another saw.

good luck on your quest to fixing it

 

[Maintenance Chief]

Is it getting hot enough to boil the fuel? Tank vent?

 

[Michael Rupley]

Quit screwing around and change the coil

 

[Lightning Performance]

I'm with Mike ^

Bad coil, cracked coil, pissed off coil?...
It is for sure ignition related. That clean kill and back again, then repeats itself.
It could also be a primary or secondary ignition lead. Go over that coil wire again. A bad end tab or breaks in the jacket cause shuttering, sputtering and fits on vibration prone tools.

 

[popopboat]

Alright! Finally gathered some time today and replaced the coil.

It was the coil!!! Runs really smoth now, cold or hot.
Thanks everyone.

 

[Vintage Engine Repairs]

Hearing that saw run gave me shivers, it reminded me of my 07 which did exactly the same thing. Turnd out to be a faulty CDI that was added by the previous owner who wanted it converted to electronic ignition. I removed it and switched it back to OEM points and it ran beautifully.
Glad you have yours sorted