Are my pistons scored? Need advice

[Wow]

^^^^^^+1
After pulling muffler. slowly pull on the starter cord, so you can view the entire piston as it moves up and down. Take some pics of piston, and post them here.

Roy

Might wanna remove the spark plug while looking at the piston. That takes the pressure off. Makes it move easily. Someone is going to toss a beer bottle at me for saying this BUT I know a guy who swore on a bible he never n el ran anything but 50:1 in his Sthil 029 and upon inspection he had some scoring. While I'm ducking dodging and hiding ill tell you this. I ran my saw today and I also mixed fuel today. I put 3.2 ounces of oil in 128 ounces of hi test non ethanol and added a tad (ole timey measurements) of lucas fuel conditioner. I've NEVER run 50:1 in nuttin. Jes my 5 cents worth. With inflation 2 cents gets ya nothing. Good day.

 

[Bob Hedgecutter]

Might wanna remove the spark plug while looking at the piston. That takes the pressure off. Makes it move easily. Someone is going to toss a beer bottle at me for saying this BUT I know a guy who swore on a bible he never n el ran anything but 50:1 in his Sthil 029 and upon inspection he had some scoring. While I'm ducking dodging and hiding ill tell you this. I ran my saw today and I also mixed fuel today. I put 3.2 ounces of oil in 128 ounces of hi test non ethanol and added a tad (ole timey measurements) of lucas fuel conditioner. I've NEVER run 50:1 in nuttin. Jes my 5 cents worth. With inflation 2 cents gets ya nothing. Good day.

You can run 50:1 and still get scoring from being too lean because you cannot tune properly, or an air leak- plenty of burned up saws because of that wee mistake, or debris entering the combustion area through faulty filtration (a Stihl speciality), or specks of carbon coming back from the exhaust port.
This is why way back in the second post someone asked for photos- clear well lit photos will help explain a whole lot as to the condition of the piston and possible causes of any damage that might be seen.
OP had better get them up quick though, before we turn it into an oil (or diesel) thread!

 

[Dudders]

Why assume piston scoring, on the basis of the symptoms described? Agreed, it could be, but maybe go for other possible causes that are easier to check first. I'd at least look first at simpler things - check air and fuel filters, mixture (check plug), blow through carb, spark strength, HT lead, change the plug, anything else. Or maybe you've done that?

 

[cgeb]

Why assume piston scoring, on the basis of the symptoms described? Agreed, it could be, but maybe go for other possible causes that are easier to check first. I'd at least look first at simpler things - check air and fuel filters, mixture (check plug), blow through carb, spark strength, HT lead, change the plug, anything else. Or maybe you've done that?

Pretty simple he thinks it was straight gassed. Pull the muffler and plug and take a look should tell you everything he needs to know. Why look in the Garage for a Frying Pan?

 

[homedad]

Does scoring on the piston ALWAYS correlate to scoring on the cylinder?

 

[SteveSr]

Does scoring on the piston ALWAYS correlate to scoring on the cylinder?

Cylinder scoring is OPTIONAL.
Aluminum TRANSFER to the cylinder is GUARANTEED which MUST be removed BEFORE replacing piston.

 

[Mad Professor]

Might wanna remove the spark plug while looking at the piston. That takes the pressure off. Makes it move easily. Someone is going to toss a beer bottle at me for saying this BUT I know a guy who swore on a bible he never n el ran anything but 50:1 in his Sthil 029 and upon inspection he had some scoring. While I'm ducking dodging and hiding ill tell you this. I ran my saw today and I also mixed fuel today. I put 3.2 ounces of oil in 128 ounces of hi test non ethanol and added a tad (ole timey measurements) of lucas fuel conditioner. I've NEVER run 50:1 in nuttin. Jes my 5 cents worth. With inflation 2 cents gets ya nothing. Good day.

I've run the same quality mix oil at 50:1 since the 1970s. I worked at a Honda/Suzuki dealership back then. Air cooled motorcycles, saws, trimmers........

Never had an oil related failure or scored a piston. That includes milling with an 066

 

[Captain Bruce]

I've run the same quality mix oil at 50:1 since the 1970s. I worked at a Honda/Suzuki dealership back then. Air cooled motorcycles, saws, trimmers........

Never had an oil related failure or scored a piston. That includes milling with an 066

40:1. The machine will either smoke or scream. Lawn Boys were 32:1, and are still out there with nice shiny cylinders and piston skirts. Oil quality has spiraled into the runway. CHEAP bottle of oil for a single gallon of fuel is a doomsday mix. Whatever happened to Optimol tubes?

 

[leeha]

Umm you don't know the dipshat that did it! LOL he tried to blame it on me, since both cans were red LOL. Yeah, I made him pay for a new topend. Husqvarna 576xp. I do all the felling, all he does is buck logs on the yard and hes tore up 10x as many saws as I have! Just in the last year hes destroyed or damaged saws 5 times. Crushed 1 with the knuckleboom, ran over 1 with the wheel loader, destroyed 2 fuel tanks on a 461 and dropped a log on 1 with the knuckleboom. Good help is IMPOSSIBLE to find!

And why the hell is he still working for you. I'd would have fired him on the second saw he destroyed not the 10th.

 

[Trailsawyer]

Family???

 

[Mad Professor]

Family???

I was thinking BIL

 

[Fatherwheels]

And why the hell is he still working for you. I'd would have fired him on the second saw he destroyed not the 10th.

He would be long gone and missing any wages he thought he would have coming.

 

[Huntaholic]

Family???

DING DING DING! We have a winner! 1st cousin actually and he doesn't technically work "for" me, he works for himself, I just furnish the saws, logging equipment, timber, etc.... he furnishes the loaders and the log trucks. I did make him pay for a new top end though. If something tears up due to use, age, etc.... that's on me. If they do something STUPID, that's on them!

 

[Oletrapper]

Btw, if that saw is anything like the 290, I found replacing the cylinder or piston to be a PITA

When it comes to repairing saws, nothing is a PITA. Just a lot of wrench throwing and beer drinking. MHO OT

 

[Oletrapper]

Oh there is "going back" it just gets expensive and mechanical.
You suspect it was run with straight gas- usually you only suspect that if you realise after something goes wrong and you remember oh damn I forgot to add the oil......
Personally I would advise not running it until you have removed the muffler, provided photos for the piston face through the exhaust port and confirmed the rings to be free and piston unscored.
If it is marked you will have to dig deeper and it is likely to cost you a piston and rings minimum, with the added bonus of having to clean any aluminium transfer from the melted piston to the cylinder walls. If you continue to run it and the mix is oil light, it might just cost you a cylinder as well, or it something lets go (busted ring or bearing) it could score the cylinder wall beyond saving.
If a saw develops an unexplained problem, better to fully investigate that problem than continue to run the saw. Many a saveable saw has been ruined over the years by people trying to tune out air leaks and keeping the saw running, repaired when first noticed- the saws would still be running, trying to tune out a fault usually ends up with a burned out top end.
As for straight gassing- most all of us have done that at least once!

Not me. Did put oil in the gas tank and mix in the oil tank once though. lmao OT

 

[Oletrapper]

Straight gas is nothing compared to DIESEL FUEL! Ask me how I know.

Me too.

 

[Oletrapper]

Easily confused by modern day kids that learn from a 5" screen.
Had it happen to me, young guy down on his luck was living with us, set him the task of mowing our lawns (4 stroke Briggs) while we were out working to support his sad ass and rather than heed the instructions about where the gas can was, he went a hunting and found a similar looking can to a gas can- but it was yellow, filled the tank, shagged the mower, went and got my other mower- filled it from the same YELLOW can and proceeded to fork it as well.
Cost me two new motors.
That kid does not live with us no more.

Sorry, but there is no way diesel fuel will destroy a 4 stroke. It will run like crap if it runs at all. Empty the tank. Drain the carb. Put in gas. Your good to go..
As far as the kid not living there anymore, well, my dad used to say "That's why they put erasers on the end of pencils."

 

[Oletrapper]

I would say that saw cant sieze on diesel....? It would be just pita to clean everything

 

[Brufab]

Curious to see the op pics.

 

[Oletrapper]

You can run 50:1 and still get scoring from being too lean because you cannot tune properly, or an air leak- plenty of burned up saws because of that wee mistake, or debris entering the combustion area through faulty filtration (a Stihl speciality), or specks of carbon coming back from the exhaust port.
This is why way back in the second post someone asked for photos- clear well lit photos will help explain a whole lot as to the condition of the piston and possible causes of any damage that might be seen.
OP had better get them up quick though, before we turn it into an oil (or diesel) thread!

Read on, That has already happened. lmao