How the hell did I kill another Stihl?

[huskihl]

Is Kevin also known as huskihl. I read his post. Then he posted a picture and blew his argument. Mechanical things fail, for a variety of reasons, oil can be one of them, and so could plenty of other reasons. If you think the problem is oil, it is oil. No need to investigate further, stop looking at the damage, it is the oil, damnit!!! Just believe me!!!!

Here's another failure caused by oil. Now in this case it wasn't just the oil mix/weight, but the brand of oil. And low tire pressure, and a dirty passenger side mirror, and a violation of the speed limit, and texting while driving, but the OIL was a factor. I know because I have seen a thing or two.

But these are chainsaws. No mirrors, tires, door latches....only air, fuel, and oil. And maybe added heat from a dull chain.

Strato saws are roughly 30% more fuel efficient, due to the spent exhaust gasses being purged out by fresh air from the strato ports rather than fresh mix from the next cycle. Therefore there is roughly that same 30% less oil and (cooling) fuel traveling through the bottom end. And strato pistons are 15-20% or so heavier than their older counterparts.
Heat and added wear are the problems. Using more oil seems to rectify it.

 

[Benjie Duke]

View attachment 799515
I wonder if this saw got used commercially, possibly to rip lumber for crating, or dunnage. The short runs could cause the saw to never warm up and create the carbon gunk.

I like your diagnosis the best.

 

[rogue60]

But these are chainsaws. No mirrors, tires, door latches....only air, fuel, and oil. And maybe added heat from a dull chain.

Strato saws are roughly 30% more fuel efficient, due to the spent exhaust gasses being purged out by fresh air from the strato ports rather than fresh mix from the next cycle. Therefore there is roughly that same 30% less oil and (cooling) fuel traveling through the bottom end. And strato pistons are 15-20% or so heavier than their older counterparts.
Heat and added wear are the problems. Using more oil seems to rectify it.

I wouldn't even bother replying to him he has nothing to add it's why he post total rubbish nothing of content for comments.
He's probably in the camp of thought that oil is abrasive like sand lol
Oh well they need people like this in the world or who else could they to sell electric cars to.

 

[Skunkdynamite]

I like your diagnosis the best.

Upon disassembly this saw was heavily abused... There's GOBS of crap in the flywheel center, behind all the nooks, under the carb, etc.
Running a few tanks of 40:1 premium mix did not kill this one...it definitely didn't save it either. I'll have it back in service shortly.
I want to wait until I get the better vac/pressure pump before I take it all the way apart to get a diagnosis.
This whole saw rebuilding thing is addictive...I know I'm going to end up rescuing more saws

 

[Skunkdynamite]

So much drama in between this breakdown and a diagnosis / repair....
Thanks to all who helped me out.
I ended up putting this on the back burner because my tractor (51 Ferguson T0 30) shat the bed... fixed the carburetor, welded the exhaust manifold back on and upgraded the intake to a K&N cone filter. 2 hours after its running I blew the top seal on the hydraulics
So I got a more modern tractor a New holland 1920 with a loader!
The mighty vac/ pressure tester proved itself immediately, there was a small cylinder leak at that location where the dust was disturbed,there was also a leak from the carburetor! Carb gaskets were stiff as a board... Replaced the gaskets with OEM parts.
New meteor piston, caber rings, gently polished the ports, unrestricted the muffler and she's running like a champ!
Perfect timing for the world to go into quarrentine... All my equipment is running

 

[RED-85-Z51]

I don't fully understand why a machine would completely crap out at 40:1, but mine was bogging sometimes at full throttle, rarely, but enough to give me a bad feeling. Switch to 50:1 and never a problem since. The ms461 runs fine with 44:1, but for the sake of simplicity it will now be fed a diet of 50:1

Carbon is really hard and modern saws are tight. Carbon builds up on the exhaust port and scores the piston

Sent from my LM-G820 using Tapatalk

 

[barebunns]

So I was just overjoyed to get my290 to 390 rebuild up and running, I made a few cuts and gave it some rest.
Fired up the 261 to lay down a few trees on the list and it stalled out on me... Weird.

Thinking about it the last time I ran it, it stalled and seemed a little weaker in the cut.
I bought it on Ebay from the seller with the fancy background... Had pics of it with a compression gauge on it. I repeated the same reading when I got it in the mail. Thought that was a good indication of internal conditions... Upon going over it, she looked a little dirtier than any saw I'd ask $400 for.
Since I got it in September I ran a quart of premix 2 stroke fuel and a tank or two of Ethanol free 91 both mixed at 40:1
Pulled the spark plug every time I ran it to check for conditions too...
It stalled mid cut on me today, just like when my 291 died... Pulled the muffler and the rings are scored and so is the piston. A littlehheavy on the carbon in the exhaust port too... I did zero modifications to this one, wanting the pro saw for the resale value when I got my other saw back together. I really don't know what the problem is here...
Can a beat up saw still have good compression for a few runs? Did I get bamboozled by a seller of junk or am I just killing perfectly good equipment?!


What the hell am I doing wrong?!?!

sthil takes 25 to one gas oil mixs

 

[grizz55chev]

sthil takes 25 to one gas oil mixs

Re-read yer manual. 50:1.

 

[Okie]

You asked:
Can a beat up saw still have good compression for a few runs?

YES

You really answered your own question.

If you cannot take a peek with the muffler off BEFORE buying you are buying a pig in a poke, especially a used saw.