husqvarna 350 grenade!

[subhunter]

The other day I had a 350 that just died after start up. It was on its third tank and just after warm up at WOT shut down. Well I could tell the verdict by pulling the cord so I just grab another saw and finish the job. Today I pulled the top end to find this.

Any ideas? The saw ran and cut good after the rebuild. Was straight gassed before and I stuck a golf piston in it. Three tanks in and this.
The ring was broke, the crown was in the muffler and the skirt was in crankcase.

 

[RTK]

My first guesses would be a defective piston or fod. I would assume the broken skirt was caused by the piston being forced to rock that way seeing the chunk out of the opposite side. How are the con rod bearings?? Can you take some pictures of the cylinder??
Either the crown broke off of the piston first and caused the skirt to break or something broke the crown off first. Where did you find the skirt??

 

[subhunter]

The bearing still seems smooth and have very little play. also the jug stills seems usable with only slight score below exaust.

Skirt was found in the bottom below piston in the crank case.

 

[mtngun]

a golf piston in it.

 

[tommymacher]

looks like the end gap swung around to the exhaust and popped the top. check if the locator pin is still there?

 

[HiOctane]

Piston was backwards,we dont see the pin locator or the pin came loose.

 

[AZLOGGER]

Piston was backwards,we dont see the pin locator or the pin came loose.

:agree2: 110%

 

[subhunter]

piston wasn't installed backward!

Piston was backwards,we dont see the pin locator or the pin came loose.

Are you saying the piston was installed backwards? Because it most definitely was not! I have yet to check the locate pin. I am out of town now until sunday and the saw is at home so I will have to wait til then to check and take a pic of the bore.
Thanks for the repiles

 

[Yoopermike]

If my memory serves me correctly the ring pin should have been on the rear OR " intake" side of the cylinder . I see no such pin in you picture of the intake side of the piston... I also think it was installed backwards (which can be easily done) or the piston itself was flawed and did not have a pin. That crown break also looks like the ring caught the bottom of the exhaust port on the down stroke and busted the top of the piston. But thats just my theory and opinion.

 

[JDNicol]

It appears the locator pin has sheared off or was incorrectly manufactured. You can just see a bit of the locator pin (however, it is masked by the camera flash), the piston was not installed backwards;

This would have caused the ring to spin around, the ring end snag on the exhaust and carnage follows.

 

[JDNicol]

Having sharpened the pic up a bit;

 

[subhunter]

Having sharpened the pic up a bit;

I appreaciate that. I couldnt take a look at the piston for days BUT I knew it wasnt in backwards.