Help with 066 failure analysis (pics)

[rupedoggy]

Actually, running more oil in the mix will cause the engine to run hotter... for five reasons.
Oil sinks less heat than gasoline as it travels through the crankcase and cylinder.
Oil burns at a higher temperature than gasoline.
Oil lowers the octane level of the fuel mix.
Even when properly adjusted for the mix, the carb will be delivering less gasoline then if it was using a mix with less oil.
Using more oil in the mix will rob power from the engine, causing it to work harder.

They say the internet will give information and some of it is false. If you think running more oil will make your saw hotter try this yourself:
Keep increasing the amount of oil until it gets hot, 16:1, 10:1, 5:1 unless you have the wrong setting on your carburetor your saw will never seize (get to hot).
As for oil burns at a higher temperature, this is not true. It may have more BTUs but oil burns slower than gasoline. It also takes more heat to burn the oil and unless you have 22:1 compression the heat isn't there (think diesel engine). You really sound like you know what you are saying, trouble is you don't. ( I do agree oil lowers the octane).

 

[mountainlake]

Haven't seen but (apparently) the exh side. I'd expect the exhaust side to experience damage first & worst anyhow.
Looks mainly like it's been dry of lube for some while under heavy load. Aka straight-gassing.

The operator was clearly not able to hear what the saw was telling him- a rookie. Straight-gassing not at all unlikely for such operators. One such fellow asked me back when "what does it mean when smoke is coming out of the saw everywhere?" Duh.

Sticking with straight-gassing by complete idjit. With a dose of leanness. And dirty cooling fins.

Not so, I've had a few that were staight gassed, damage is even all the way around the piston. This is a lean sieze for what ever reason. Steve

 

[sachsmo]

speaking of temp monitoring, Bob L in the milling section has used these. And yes milling is torture for saws.

I run good synthetic at 32:1 and have never had problems, 50:1 might be enough for the cylinder, but the bearings need good lube too.

Someone saw this early on in the thread, does not look like aluminum.

The porous area above the ring land looks to be bad casting, seems to be a classic lean seize/bad gas.

 

[coyote556]

First off, I would like to thank everyone for all the input and help. You all made me want to look closer and I noticed this, the finish inside the crankcase has been flaking. I have attached additional photos for more ideas. I have definitely rulled out the straight gas. I have had this thing apart for a few days and there is still liquid oil from the fuel mix visible. I dont think there would be had it burned up on straight gas. See the pics below.

 

[coyote556]

 

[Whitespider]

They say the internet will give information and some of it is false. If you think running more oil will make your saw hotter try this yourself:
Keep increasing the amount of oil until it gets hot, 16:1, 10:1, 5:1 unless you have the wrong setting on your carburetor your saw will never seize (get to hot).
As for oil burns at a higher temperature, this is not true. It may have more BTUs but oil burns slower than gasoline. It also takes more heat to burn the oil and unless you have 22:1 compression the heat isn't there (think diesel engine). You really sound like you know what you are saying, trouble is you don't. ( I do agree oil lowers the octane).

I said more oil will cause the saw to run hotter... I didn't say it would make it hot enough to seize.

Before you start saying someone doesn't know what they're talking about, and then trying to use facts to make your argument... well, you really should check your facts. Under atmospheric conditions the flame temperature of gasoline is right at 3500[sup]o[/sup], and the flame temperature of most any oil is right close to 3800[sup]o[/sup], a full 300[sup]o[/sup] hotter than gasoline. Of course both those numbers change when under pressure in an engine cylinder... but the oil still burns hotter.

Yeah, a puddle of oil burns slower than a puddle of gas... but the stuff is vaporized in an engine. Besides, if the oil is burning slower... well then the flame would have more time to heat the surrounding metal... correct? So now we have a hotter flame, burning for a longer duration... yep, I'm pretty sure that should heat the metal more.

So you really think the compression of a diesel engine generates more heat the the tip of a spark plug? Or how about the temperature of the spark itself? Let's see now, the tip of a spark plug runs between 1200 and 1500 degrees, and the spark itself is several thousand degrees... WOW! that diesel engine must be made of some super space-age material... wish I had some of it.

I won't go so far as to say you don't know what you're saying (like you did about me)... I'll just say I think you're a bit confused about the chemistry dynamics at work in an internal combustion engine.

 

[Whitespider]

First off, I would like to thank everyone for all the input and help. You all made me want to look closer and I noticed this, the finish inside the crankcase has been flaking. I have attached additional photos for more ideas. I have definitely rulled out the straight gas. I have had this thing apart for a few days and there is still liquid oil from the fuel mix visible. I dont think there would be had it burned up on straight gas. See the pics below.

coyote, in your original post you said the damage looked like some detonation photos you found (Madsen’s?). For some reason you tossed it out to the board for opinion… and as expected you get near every conceivable opinion.

Bad gas… too much water in it
Straight gas
Ethanol
Heat seize
Not enough oil in the mix
Detonation
Pre-ignition
Lean seize
Piston corrosion from sitting with water on it
Casting flaw
Wrong spark plug
Fuel octane too low

I think you can pretty much rule out straight gassing and not enough oil as the cause, your pictures show plenty of oil residue on the crank, rod and inner piston around the wrist pin.
A wrong spark plug should be easy enough… it either has the correct plug screwed in or it don’t.
Pre-ignition is doubtful, should be more damage, like something broken.
Piston corrosion from sitting with water on it? Hmmmmm, that’s an interesting notion, one I wouldn’t have thought of, but I don’t see any other evidence (such as rust) in your pictures… still, it’s an interesting notion.
Both lean seize and heat seize are possibilities… except that that eroded-away/blasted-away area on the piston corner indicates something else got the problem started.
Some believe that eroded area looks like a casting flaw, to me it looks like it’s been blasted away by detonation (and the associated heat). Detonation is normally initiated because of too much heat and pressure for the octane level of the fuel… not necessarily abnormal heat, but once detonation starts the engine temps rise rapidly. The detonation began blasting away at the piston and increasing temperatures, once the damage reached the ring it froze. And once the ring froze… So yeah, bad gas or low octane or ethanol or a combination of any of the three could have initiated the detonation… but without testing the fuel for octane level, ethanol content and water you’ll never know for sure.
Somewhere in this thread you indicated a belief that the guy was running ethanol-blended 87 octane fuel… and the internal engine damage (in my opinion) looks like detonation was at work. Maybe a richer carb setting would’ve saved the saw, maybe… we’ll never know. I will say that ethanol has been long known to attack metal and engine coatings (like in your picture of the crankcase)… but again, that ain’t necessarily proof, just more evidence.

Fix the saw, maybe teach the guy to tune it just a hitch on the rich side, and strongly suggest he run a higher octane fuel… preferably ethanol-free if he can get it.

 

[coyote556]

What's is your opinion on that paint coming off on the inside of e crankcase? Does it even matter?

 

[RAMROD48]

What's is your opinion on that paint coming off on the inside of e crankcase? Does it even matter?

Only when running at say...speeds a saw runs at....:msp_biggrin:

 

[kevin j]

another left field idea, triggered by the flaking paint inside, and what looks in the pic to be some porous surface of the piston on the intake side pic, lower left skirt. Or is that photo effrects?

Has the owner run any additives in the fuel that could be chemically active? too much stabil, Heet, or something like that?

I am still in the 'too much heat' column though.

 

[Whitespider]

I am still in the 'too much heat' column though.

The problem with blaming "too much heat" as the root cause of catastrophic engine failure is that it's actually a symptom, or result, of something else. "Too much heat" doesn't help diagnose what went wrong... an engine just doesn't get too hot unless something else causes it to happen. For example, plugged cooling fins, a lean condition, a rich condition, not enough oil, detonation, restricted exhaust, a failed bearing, over-loading, bad fuel, plus any number of other things can, or will, cause an engine to get too hot.

It's obvious that at some point that engine experienced way "too much heat"... but the million-dollar question is, why?

 

[lone wolf]

The problem with blaming "too much heat" as the root cause of catastrophic engine failure is that it's actually a symptom, or result, of something else. "Too much heat" doesn't help diagnose what went wrong... an engine just doesn't get too hot unless something else causes it to happen. For example, plugged cooling fins, a lean condition, a rich condition, not enough oil, detonation, restricted exhaust, a failed bearing, over-loading, bad fuel, plus any number of other things can, or will, cause an engine to get too hot.

It's obvious that at some point that engine experienced way "too much heat"... but the million-dollar question is, why?

Simply, lean tuning on the H is the first thing to look at.