Someone please tell me I didn't burn a piston

[The Abominable Snowman]

That's really all I want to hear

Short story: Opened up the exhaust port to about twice what the stock hole was. Then tried to retune the carb. Low adjustments went fine. But then while doing the high adjustments, the saw shut off with no explanation.

Longer story: Decided I waned to get set up for milling (Alaskan). Decided I needed a big saw to do the job. An 088 popped up on CL so I grabbed it. Not a crazy deal, but it seemed reasonable. The guy fixes saws for fun / extra cash. On this one, he had replaced a flywheel and piston. We fired it up when i bought it. Seemed great. Didn't run it very long. Took it home. I never got to actually cutting anything with it. But I did get around to grinding out the exhaust hole. It just seemed so easy on this saw, I couldn't help myself. Even though I have very little actual experience with saws, so I probably had no business doing that. But like I said... seemed like it was too easy NOT to do. After that I tried to retune the carb. Low adjustments went fine, though i couldn't quite get it to idle without the chain rolling a bit. But I moved on to the high adjustment. I know I started lean, but I tried to move quickly toward rich out of fear of causing piston damage. I thought I was getting into the right range, but then the engine quit. This took place after the saw was at full throttle for maybe 30 seconds. Wouldn't start back up until it cooled down for a while. Then the same thing happened again. Third time, it wouldn't start back up.

Any thoughts? I know it could be a lot - coils, spark plug come to mind. I'll probably get some help from the local dealer or the guy I bought it from, but just wanted to see if anything sounds obvious to you lovely people... I couldn't have cooked the piston that quickly (in a matter of seconds) running too lean, could I?

 

[Robin Wood]

i dont think you can fry a piston that quick, but it does sound like heat issue
how's the compression ? is resistance from pulling the starter handle strong ?
you mention that you couldnt get the idle right, it could be due to air leak
im sure the pros will chip in soon, gotta wait for it

 

[The Abominable Snowman]

some background, which I feel I owe you since I've been trolling on here for a while...

I'm not a pro. Not even close. I do some work for family and friends, mostly trimming high branches via DRT. Some felling. This milling thing is new for me. Owning such a serious saw is also new territory for me. That's why I'm overly concerned about breaking it

 

[The Abominable Snowman]

how's the compression ? is resistance from pulling the handle strong ?

Haven't taken compression. Pulling the rope feels normal though.

 

[Robin Wood]

Haven't taken compression. Pulling the rope feels normal though.

i assume the saw doesnt have a bar mounted on it, try letting off the saw slowly while holding the starter handle and see if it drops quick or slowly
guys here call it the compression drop test, where if drops quick and with no resistance then its got bad compression
i believe you said the saw wont start at all now. does it has spark ? test it if you havent

 

[Big_Wood]

even a saw that was badly torched and has interference between piston and cylinder due to scoring can feel like it has compression. the fact he replaced the piston is scary as he may not have fixed the original issue or even cleaned up the cylinder properly for that matter. pulling the muffler for inspection would be the first thing i'd do.

 

[HarleyT]

Yes, it is that quick and easy to melt your piston, you can do it with a brand new saw too.


Easy also to take off the muffler and take a peek.

 

[CoreyB]

Also did you rinse the muffler out after cutting on it or did you expect all the metal shavings to just blow out?

 

[Robin Wood]

Also did you rinse the muffler out after cutting on it or did you expect all the metal shavings to just blow out?

uh oh, hope he did
coz if he didnt, its gonna scavenge the debris in

 

[Big Block]

uh oh, hope he did
coz if he didnt, its gonna scavenge the debris in

 

[The Abominable Snowman]

This muffler has a separate plate for the exhaust hole. Shavings shouldn't be an issue. Unless something else got in the muffler while it was sitting on my bench. I'll take a peak inside... What exactly am I looking for? Should it look like nice shiny metal?

 

[The Abominable Snowman]

 

[The Abominable Snowman]

I also noticed that it makes a creaking sort of sound as I pull it. Is that normal, or is that bad?

 

[Robin Wood]

thats not how new piston should look, its scuffed
at this point i think you might as well take out the cylinder and take a good look at the muffler side wall and if its damaged, well i hope it doesnt then im afraid you gotta get a new cylinder
someone pro should handle this case, im not too familiar with these things

 

[HarleyT]

I also noticed that it makes a creaking sort of sound as I pull it. Is that normal, or is that bad?

Likely metal/metal contact....
Not good.

 

[The Abominable Snowman]

Ugh. Ok, thanks. I don't have the tool I need to get the cylinder off. I think it's officially time for a trip to the shop...

 

[Marshy]

Ugh. Ok, thanks. I don't have the tool I need to get the cylinder off. I think it's officially time for a trip to the shop...

If you don't have the tools to take the cylinder off then how exactly did you grind the exhaust port, with the cylinder still on the saw? Sounds like you probable F'ed it up with your shade tree port job. Live and learn.

 

[Rockjock]

If you don't have the tools to take the cylinder off then how exactly did you grind the exhaust port, with the cylinder still on the saw? Sounds like you probable F'ed it up with your shade tree port job. Live and learn.

 

[Definitive Dave]

Clip on muffler
I am assuming you pulled the muffler to grind the exhaust and cleaned it out before reinstalling right?
Piston don't look good, there are aftermarket Pistons of varying quality, hopefully the seller used an OEM for a saw this size/price.
Find a solid member close by to help you out. Hopefully cylinder can be salvaged

 

[stihl sawing]

If you don't have the tools to take the cylinder off then how exactly did you grind the exhaust port, with the cylinder still on the saw? Sounds like you probable F'ed it up with your shade tree port job. Live and learn.

And there's your answer, I'm no mechanic but if you grinded on the port with the piston still in, then the shavings screwed the saw.