Trusting the Sniff Test...

[Mat H.]

How long did it run before the damage occurred? I would have expected to see a lot more piston damage. I see the damage to the cylinder port - that is the intake port, right? Looks like something was sucked into the intake.
View attachment 769670

Had run the saw for 1/2 hour, maybe. It quit and when I tried to start it I felt it catch and then would not budge. In hindsight, I wished I had taken the carb and exhaust off first. Muscled the head off which explains the damage to the intake port.

 

[Gord404]

Might be a chunk of bearing cage, worth a careful inspection speaking from experience a few years back

 

[BangBang77]

Yeah, that doesn't look straight-gassed to me...not saying you didn't have straight gas in it, but the failure was mechanical in nature.

 

[Capitalist]

I tried this.
I got a jug of mixed and a jug of straight.

I smelled each.

I really couldn't tell.

So I did it five more times.
Everything started buzzing and my cat turned into a jackolantern.

 

[farmer steve]

I tried this.
I got a jug of mixed and a jug of straight.

I smelled each.

I really couldn't tell.

So I did it five more times.
Everything started buzzing and my cat turned into a jackolantern.

What kind of oil in the mixed jug? And what ratio?

 

[Capitalist]

What kind of oil in the mixed jug? And what ratio?

I dont know let me smell it again at different ratios.
Think it was 50:1

 

[Moto Vita]

Intake side. But I do know, for sure, that it was unmixed gas.

How do you know that now? Straight gas damage should show on the other side of the piston, what does it look like?
I'm wondering what oil you use that you can smell over gas fumes.

 

[Gord404]

I guess my way of always telling is I have a big container of straight gas marked straight gas and 2 small jugs marked mixed, - pretty hard to go wrong.

 

[bwalker]

As others have said that saw doesnt appear to be straight gassed at all. Looks like you broke a ring and that's what caused your problems.
Also RTV is not gasoline resistant and is not the thing to use on anything that comes in contact with gasoline like a base gasket.

 

[full chizel]

Just stick your finger in it. If it is straight gas it will evaporate completely, if it’s mixed the gas will evaporate but the oil will not, leaving oil on your finger

 

[HarleyT]

Just stick your finger in it.

Advice to use in all facets of life......

 

[grizz55chev]

Advice to use in all facets of life......

That’s what she said!

 

[Bobby Kirbos]

In the future if you're not sure, dump the unknown fuel into the lawn mower can and make up a fresh batch of 2-stroke mix.

"waste" a few ounces of 2-stroke oil --- OR --- rebuild the top end on a chainsaw

Wasting a few ounces of oil is both easier and cheaper than doing an engine rebuild.

 

[Huskybill]

Shake up the gas can that has mix in it before pouring. The two stroke oil separates from the gas even over night. Shake it, shake it good.

 

[Bobby Kirbos]

Not passing the sniff test for sure. I think something else happened.

I suspect that the locating pin broke or backed itself out, allowing the lower ring to rotate. Once it rotated enough, it grabbed the port... and the rest is history.

It is possible that the ring overheated and broke due to insufficient/no lubrication, but I would expect to see more wear on the piston and cylinder wall if that happened. The lack of wear makes me believe that the above hypothesis may be more likely.

 

[Vintage Engine Repairs]

If it ran for 30 mins, you would have had oil in the mix!

 

[Marley5]

I can close my eyes and tell if it's 50:1, 32:1 , synthetic mix or trufuel......don't smell it, taste it.

 

[Mad Professor]

Looks like a ring broke. Pin is still in place.

A piece of bearing or other ingested crap would have left a score/gouge on the piston.

 

[Nathan Graff]

Could be that the ring cracked during assembly, and it took till now for it to work it's way loose.

 

[HarleyT]

It should be covered under warranty!!