066 Epic Piston Fail & Carnage

[Brmorgan]

Is that what that is? I was wondering since I'd never seen one before.

 

[056kid]

Yeah, like I said I'm sure it was hot with all that crap built up on the cylinder. But I'm just surprised the piston would disintegrate without there being any aluminum transfer to the cylinder if it was just heat.

It's impossible to tell now, but I wonder if the piston wasn't just worn right out and sloppy, and maybe was able to "rock" enough to snag the exhaust-side skirt on the bottom of the exhaust port. Just a theory. That would probably transfer enough energy up the side of the piston to snap it at the windows. I'll have to have a closer look at the port.

I think if the piston was slapping, even for a short time, it would have left some marks on the jug which looks awesome..

 

[Brmorgan]

I think if the piston was slapping, even for a short time, it would have left some marks on the jug which looks awesome..

I would think so too, but what else would do it? There's no other heat damage, and there was obviously not any foreign steel from a bearing etc. otherwise the cylinder would be bashed up.

So, I guess I should ask for recommendations on the best option for a piston here. If everything else on the saw is good when I rip it down, I might spring for OEM if the price is right. Failing that, who's got the best aftermarket? I was impressed with the Episan I threw in a friend's 034 - it looked identical to the original in pretty much every regard, and the saw's running really well with it. Thoughts?

 

[Jacob J.]

Hm, didn't notice it as a redlight but I've only seen a couple in pictures and to be honest I wasn't really looking out for it. I'll check it when I go down to stoke the fire in a bit.

Yeah, it was a pretty good day! Went to work with two saws and came home with 6 for $120, including a couple real gems. My birthday isn't for another five months!

That one is from the era just after the release of the first polymer flywheel saws. So you have a flat-top polymer flywheel 066 that has the compression release and the crankshaft with the larger big end bearing and flywheel side stub shaft.

Flywheel side bearing will be a 6203...

PTO side is proprietary.

 

[ironman_gq]

meteor from Bailey's $40 OEM from Bailey's $140. from what I hear the meteor pistons are very close if not just as good as OEM for less than 1/3 the price. I hear they are getting weisco pistons too just not sure for which saws yet. might be something to look into as they would probably be of even better quality than OEM and probably forged too.

 

[wigglesworth]

That is an epic fail. I wonder what the cause was????

 

[Tzed250]

.


Piston failure like that is due to excessive RPM many times. The skirt fatigues and cracks, then separates.


.

 

[timberwolf]

With the polishing of the edge of the crown and by the general look of things the piston had a few hours on it. Likley was bouncing about pretty good in the bore putting a pounding on the skirts til something gave.

 

[Miles86]

Thast inpact mark look link a needle bearing got trapped and fractured the whole piston. Count the number of needles and check the needle cages?:jawdrop:

 

[Arrowhead]

Brad, You got a heck of a deal! I would lightly sand the cylinder, then through a Meteor in it. Cool pics.

 

[jd548esco72]

Brad, You got a heck of a deal! I would lightly sand the cylinder, then through a Meteor in it. Cool pics.

+1 good score!:greenchainsaw:

 

[ironman_gq]

hows the top of the chamber look. Looks like you got lucky and it stopped up tight and fast before the crank got around a few times and really beat it up bad. Usually if they go like that the pin hole doesnt blow out like yours and the piston makes it around a few more times before the engine locks up and usually beats something (ring piece, end pin, beraing, etc..) into the top of the piston and chamber.

 

[Teddy.Scout]

Dont look like a red light to me. Whats the big deal with you and red lights?

I am not a Chainsaw Tech.!!!!

So it is nice to have something that is rev. limited, so it may save me the hassle of blowing up a saw! And with the rev. limiter, I was able to mill with it, before I could afford a large 100+cc saw! So they have a place in my collection!

Granted the reason for the red light, (for what I understand!?) was that the lower ends kept breaking down!

 

[logging22]

I watched a guy put the end of a pair of pliers into the plug hole once for a piston stop. On a 288. Taking off the clutch to replace the rim. Put a ratchet and socket on it and hit it with a hammer. Thats what the piston looked like after.

 

[DSS]

What, you couldn't wait to find one in the garbage so you had to go buy one?You got to be the luckiest :censored:hole I ever heard tell of. I wish we lived closer so I could buy you a beer.......Congrats again.

 

[Sprintcar]

Check the rod end play and look at the crank throw for any witness marks.

I saw an 066 that did that once.

 

[Brmorgan]

hows the top of the chamber look. Looks like you got lucky and it stopped up tight and fast before the crank got around a few times and really beat it up bad. Usually if they go like that the pin hole doesnt blow out like yours and the piston makes it around a few more times before the engine locks up and usually beats something (ring piece, end pin, beraing, etc..) into the top of the piston and chamber.

The top of the chamber looks perfect except for some carbon buildup and what look like possible minor detonation marks in the combustion chamber. I'll try to get a pic of it.

The pin boss isn't blown out; just the window on the exhaust side. I took a few more closeup pics of the piston tonight:

There is a lot of friction wear on the break that's in the foreground in this photo - it's definitely not a fresh break like the other side.. This suggests to me that this side of the skirt broke a while before the piston failed completely. There is also significant wear below the bottom ring to the left of the remainder of the window in the photo.

There is a bit of roundover on the crown on the intake side from running with a lot of piston slop. Not as much as the other side though:

Look how much the crown is swaged out from impacting the top of the cylinder! I don't know if that's all from one big final impact when it blew up, or from repeated impact while running.

I just can't believe how deformed this side of the piston is. Especially without causing any scoring or other damage to the cylinder. It's starting to look like the lower part of the casting that connects the skirt to the pin boss below the window broke first, allowing the skirt to flex and cause the extreme wear.

I watched a guy put the end of a pair of pliers into the plug hole once for a piston stop. On a 288. Taking off the clutch to replace the rim. Put a ratchet and socket on it and hit it with a hammer. Thats what the piston looked like after.

Wow, that's a bonehead move. Maybe if the piston was solid that would work! Was it one of those moments where you felt you should say/do something to intervene but part of you couldn't help watch a disaster in progress?

Check the rod end play and look at the crank throw for any witness marks.

I saw an 066 that did that once.

Well the crank and bearings felt nice and tight when I was working on it, but it'll get a good inspection when I do a full tear-down.

 

[eyolf]

With the amount of dust inside the saw, I'm amazed it wasn't cooked, bad.

I siezed a saw with a lot less crap than that. That dust looks a lot like one of two things we occasionally see in MN...when a red oak dies of internal fungus rot, you'll bring up a cloud of fine red dust like that when cutting. Same thing when cutting up old cedar utility poles for fence posts.

Since Oak isn't common where Bmorgan is from, I'm guessing pacific coast cedar? And a sawyer that didn't have access (or desire) to an air compressor. There's red dust on the piston: is that settling on from the outside, or did the air filter fail?

 

[MR4WD]

looks like it spent a lot of time milling prior to getting passed onto the pawnshop. Maybe it never got the heat up/cool down cycles it needed? I'd like to find an 066 like that to build for myself though.

 

[Brmorgan]

With the amount of dust inside the saw, I'm amazed it wasn't cooked, bad.

I siezed a saw with a lot less crap than that. That dust looks a lot like one of two things we occasionally see in MN...when a red oak dies of internal fungus rot, you'll bring up a cloud of fine red dust like that when cutting. Same thing when cutting up old cedar utility poles for fence posts.

Since Oak isn't common where Bmorgan is from, I'm guessing pacific coast cedar? And a sawyer that didn't have access (or desire) to an air compressor. There's red dust on the piston: is that settling on from the outside, or did the air filter fail?

Nope, I'm 99.99% sure it's Douglas Fir bark dust. It's the bane of chainsaws out here. It's as fine as flour and gets in spots you didn't know your saw had, and will cook up really nice and hard with heat and oil. Very similar to rot dust, but IMO worse.

Thast inpact mark look link a needle bearing got trapped and fractured the whole piston. Count the number of needles and check the needle cages?:jawdrop:

Well, I've worked on a couple trashed saws due to failed needle bearings, a couple from failed ring locator pins, and one which looked like a broken spark plug electrode. All three cylinders were absolutely FUBAR. This one doesn't have a scratch on it.

What, you couldn't wait to find one in the garbage so you had to go buy one?You got to be the luckiest :censored:hole I ever heard tell of. I wish we lived closer so I could buy you a beer.......Congrats again.

LOL coming from an east-coaster I'll take that as a compliment!

Lucky, blessed, I dunno what it is, but I'll take it!