Weird piston action in a blown Stihl 500i

[singinwoodwackr]

Dealer has never seen a piston do this. They sent this vid to the district mucky muck but no word as yet. Anyone ever seen this?
year old tree service saw. Always run with the new, recommended Stihl mix oil at 50:1.
I’m waiting to see if Stihl will do anything, warranty wise…doubtful…before tearing it down.

 

[ericm979]

Is that with the spark plug in or out? If the plug is out then there's probably debris in the bearings or perhaps the crankcase and it's jamming things up.

I'd expect a dealer to have removed the plug to turn the engine over but they might have been in a hurry.

 

[singinwoodwackr]

Is that with the spark plug in or out? If the plug is out then there's probably debris in the bearings or perhaps the crankcase and it's jamming things up.

I'd expect a dealer to have removed the plug to turn the engine over but they might have been in a hurry.

I called her . That vid was with plug in. She pulled the spark plug and tried it again…no change, still does the bounce.

 

[jellyroll]

Jeez.

 

[Tobystihl]

That's crap on top of the piston being squished, probably a bit of bearing....

 

[ZeroJunk]

You do realize people will lie to you about mix or mistakes ?
Nothing is 100% , but that possibility is there.

 

[ZeroJunk]

Dealer has never seen a piston do this. They sent this vid to the district mucky muck but no word as yet. Anyone ever seen this?
year old tree service saw. Always run with the new, recommended Stihl mix oil at 50:1.
I’m waiting to see if Stihl will do anything, warranty wise…doubtful…before tearing it down.

BTW, I see them every day. It's called straight gassed. Nothing special about it.

 

[cookies]

bearing cage failure

 

[singinwoodwackr]

Well, I know it isn't a mix issue as I've seen what he uses and how he mixes it.
If a bearing cage failure, would that be the crank rod or one of the side bearings or both?
Still waiting for the district Stihl rep to chime in on this.

 

[singinwoodwackr]

Looking at the piston I'd say straight gas but if that were the case there would be 6 saws blown up the same way from the crew that day as they all get gassed with the same 5gal mix can.

 

[singinwoodwackr]

P&C are around $360 but I'm betting there is a lot more damage here than just that.

 

[ZeroJunk]

Looking at the piston I'd say straight gas but if that were the case there would be 6 saws blown up the same way from the crew that day as they all get gassed with the same 5gal mix can.

Well, if Stihl warranties it, that is all that matters.

 

[huskihl]

You can’t tell if it was straight gassed without looking at the intake skirt. Straight gas scores all the way around.

I’ve seen several 500’s do that. The fuel values get scattered and it can’t recover. Needs reset with the MDG software after the scored parts are fixed.

 

[The Stig]

Dealer has never seen a piston do this. They sent this vid to the district mucky muck but no word as yet. Anyone ever seen this?
year old tree service saw. Always run with the new, recommended Stihl mix oil at 50:1.
I’m waiting to see if Stihl will do anything, warranty wise…doubtful…before tearing it down.

Try rocking the flywheel back n forth. (Free play). Possibly rod bearing gone

 

[huskihl]

The clunking when rotating the fw is from the generator underneath

 

[singinwoodwackr]

Well, if Stihl warranties it, that is all that matters.

not gonna hold my breath, lol

 

[singinwoodwackr]

Great replies, thanks!

I will most likely get the saw in my shop and will be able to post better info then. At the moment we are waiting for Stihl...cue Jeopardy theme, in slow mo...

 

[singinwoodwackr]

You can’t tell if it was straight gassed without looking at the intake skirt. Straight gas scores all the way around.

I’ve seen several 500’s do that. The fuel values get scattered and it can’t recover. Needs reset with the MDG software after the scored parts are fixed.

Did Stihl help at all with the ones you repaired? Maybe a percentage on parts, anything? This is a tree service saw, 15 months since it was bought, new. I certainly wouldn’t expect full warranty but if this is a glitch known to them they might at least cover something.

 

[huskihl]

Depends on the dealer and customer, how good of a dealer and how good of a customer. I’ve heard of them fixing stuff just outside the warranty and I’ve seen them blame it on straight gas at 3 months old.

I’d just clean up the cylinder and put a $100 oem piston in it. And have the dealer recalibrate it

 

[chipper1]

Dang stihls