WTF happened here?

[SEAM]

I sold this 024 AV Super to a guy in a nearby town about 3 years ago. He called with a "saw don't turn over" and this is what I found in the crankcase:







All bearings seem to be fine, there is absolutely no scoring whatsoever, the rings look OK, cylinder is salvageable (no scoring at all and no marks around the ports that might indicate a clip had come off or the like).

The saw was old but hardly used, pressure-tested OK and was in overall perfect shape when I sold it.

Any ideas what may have caused this? I am at a loss...

 

[old-cat]

Gremlins!

 

[lone wolf]

I can speculate and suggest the piston wore out a lot slapped and cracked then hand grenaded.

 

[Chris-PA]

Is the edge of this fracture of the pin boss polished?

 

[o8f150]

bought it 3 years ago?????? yep,,, it still should be under some kind of warrenty

 

[a. palmer jr.]

Do you think it will buff out?

 

[lone wolf]

Do you think it will buff out?

yup the cylinder will.

 

[Gypo Logger]

Defiantly oil related. Was he using Stihl mix?

 

[Landmark]

Rocket fuel?

 

[lone wolf]

i'm winning so far.

 

[rattler362]

I tore down a 281 that was not quite that bad. Be sure and check the rod bearings if little bits got in them they could be damaged too.

 

[banditt007]

A worn skirt supposedly will allow the piston to rattle in the bore, eventually crack and fail. I don't have personal experience with it but thats what i've read before looking up failures of 2 stroke engines...

 

[lone wolf]

A worn skirt supposedly will allow the piston to rattle in the bore, eventually crack and fail. I don't have personal experience with it but thats what i've read before looking up failures of 2 stroke engines...

Its a fact Jack. http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

 

[redoakman]

that looks handy by any chance could it be a case of bad casting

 

[lone wolf]

that looks handy by any chance could it be a case of bad casting

Maybe China crap.

 

[Nitroman]

Piston slap. It happens. That would have made a really nasty sound.

How about a photo of the top of the piston?

If you buy another piston, and the jug is good, I'd definitely check the skirt to cylinder clearance. If too big, you can have the piston built up to make it up.

Also check out-of-round.

 

[1Alpha1]

It's a chainsaw. That's what chainsaws do. If something unexplainable happens to a piece of OPE, it's going to be a chainsaw. I mean come on, how many times do we read about a string-trimmer, hedge trimmer, or a blower blowing up? I'm sure that it happens, but not on the scale of the saws. And yes, I'm aware that saws get used harder and longer.

As much as I like my OPE, I'm pretty much convinced that it's not all that well designed, engineered or manufactured. Too many little glitches that seem to be on-going issues and problems. Things that the industry doesn't seem to care to address.

Thing that rubs me the wrong way the worst, are the prices that the manufacturers get for them. We all know what I mean by that.

Just to be fair and balanced, I myself have never had a piece of OPE blow up. I don't know if that's just luck or the way I care for my OPE. Maybe a little of both......perhaps?

 

[a. palmer jr.]

That's what pistons used to look like in the late 70s in the fuel dragsters when they used a bit of Hydrazine for fuel. It's since been banned.

 

[Duke Thieroff]

Likely skirt wear and eventual fatigue of the casting leading to failure.

Measure the old piston skirt and compare it to the replacement.

 

[AKDoug]

I've got a box of five 026's that have pistons on the intake worn paper thin. So much that the pistons were rocking in the bore and contacting the squish band.