What weoyuld cause this?? (pics)

[snapped finger]

A friend gave me a Husqavarna 350. He loaned it to his brother and it never ran after that. Is this from gas with no oil? the cylinder walls are spotless. the damage on this piston is on the intake side and the top is pitted terrible.

 

[nmurph]

Crappy, old fuel????

That pitting on the top is from detonation.

 

[DSS]

Crappy, old fuel????

That pitting on the top is from detonation.

Yeah. And damage to the intake side usually means the saw swallowed something. Was there an air filter in it?

 

[nmurph]

Yeah. And damage to the intake side usually means the saw swallowed something. Was there an air filter in it?

Yep, but strange it would have both pitting and scoring only the intake. Scoring on the intake can also indicate no oil in the mix. Maybe he ran it with crappy straight-gas.

 

[DSS]

And how come it's only gouged halfway down ?

 

[tree monkey]

Crappy, old fuel????

That pitting on the top is from detonation.

your wrong
most likly a bearing failure

 

[ft. churchill]

Notice how the pitting is concentrated in the squish zone of the chamber, another indicator of detonation. Perhaps the detonation started on the exhaust side of the chamber (the hottest portion of the chamber) and this detonation wave traveled towards the opposite wall. That would rock the piston towards the intake side of the piston and since the detonation would occur about at the same number of degrees from TDC that may account for the line partway up on the intake skirt of the piston.

 

[snapped finger]

The bearings dont seem to have any play in them, I know the guy who gave me the saw and I know the thing doesnt have 20 hrs at most on it. He said it ran fine till he loaned it to his brother. Now he understands why I dont borrow mine out. Im gonna order a new piston and see what happens. I was just wondering if them pits are from melting being to lean or from no oil in the fuel.

 

[K.C.]

Take my advice with a grain of salt but the last time I saw something like that was in a kart engine that had sucked up something.

 

[RBurtcher]

Poor thing looks like it was run hard using keroseen.

What was the compression number? 35?

I think I would also opt for a new upper bearing.

 

[K7NUT]

X Now he understands why I don't borrow/loan mine out.

I don't care if I'm called an A&$hole, I DO NOT loan out my saws!
I worked hard to get them and believe you me, they work hard for me and I appreciate them all winter long!

Case in point(see pic of piston above)...

 

[Dan_IN_MN]

 

[Dan_IN_MN]

your wrong
most likly a bearing failure

The bearings don't seem to have any play in them, I know the guy who gave me the saw and I know the thing doesnt have 20 hrs at most on it. He said it ran fine till he loaned it to his brother. Now he understands why I dont borrow mine out. Im gonna order a new piston and see what happens. I was just wondering if them pits are from melting being to lean or from no oil in the fuel.

From which crank? It looks like it's only been run on one...????

 

[bezza1]

i had a saw with the same problem the wrist pin bearing collapsed and got on top of the cylinder

 

[snapped finger]

Thanks Bezza, that is exactly what it looks like. I will have to check it out when I get home.

 

[Jeff Lary]

What is " Detonation " ?

Crappy, old fuel????

That pitting on the top is from detonation.

Murph what is detonation ? and what causes it ?