066 Epic Piston Fail & Carnage

[Brmorgan]

Dropped by the pawnshop today and they had this 066 sitting there:

I spotted that "Parts Saw" sticker right away; like a moth to the flame! There was no price on it, so I gave the starter a pull. Or at least tried to - it was locked right up. So I asked the owner what he was hoping to get out of it. He said he turned down an offer of $75 and was hoping for $100. SOLD! If nothing else the outer parts and paint are in MUCH better condition than the tired old '66 I've been running, and I've been wanting a 3/4 wrap handle for mine anyway. I wasn't worried about losing money on it and had no problem with the hundred bucks.

Thought I'd pull the muffler quickly and see what I could see tonight:

THAT'S never good! Big ol' chunk of aluminum sitting in the muffler.

So I pulled the back section of the muffler:

Wow, talk about freeporting! After seeing this I wasn't satisfied and was compelled to pull the jug to see just how bad it was.

 

[056kid]

Great looking outside, more inside pictures please

 

[parrisw]

OUCH!! curious to see what's inside.

 

[Teddy.Scout]

Is that a red light to boot!!!!!!!!!!!!!!

WOW! you have all the luck!

 

[Brmorgan]

Well, here's how bad it was:

That's got to be one of the worst, if not THE worst, piston self-destructions I've seen. Not that I've seen that many compared to a lot of you guys, but still. Pretty savage. What would cause that? The intake side skirt has quite an impact mark on it, but I'm pretty sure that's a result of it snagging a piece of the exhaust-side skirt in the intake port when the thing grenaded. The rings are stuck pretty hard too.

Now here's the kicker:

The cylinder's still in really good shape. There are a couple minor scuffs around the exhaust from me forcing the piston out, but they'll be fine after a light sandpaper treatment.

I'm wondering, am I wrong in thinking this is a fairly old 066? That exhaust port looks pretty big, and is just about as wide as possible gauging by the skirt marks in the cylinder (about 1/16"), and it sure looks stock - the chamfer is perfect, as is the port itself. Very good work either way. The intake still has casting lines visible in its roof, so I'm certain it's stock. It could be widened a bit still though if the rings allow. I've never worked on 066 cylinders before.

Can't say I'm surprised this piston blew up with how much gunk was caked all over everything:

Still, I don't know why it would have exploded like that and not scored anything at all. Glad I wasn't holding onto it when it happened though!

 

[mtngun]

I wouldn't mind having a $100 066 project saw.

Keep the pics coming. opcorn:

 

[Brmorgan]

Is that a red light to boot!!!!!!!!!!!!!!

WOW! you have all the luck!

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!

 

[Zuni]

I wouldn't mind having a $100 066 project saw.

Keep the pics coming. opcorn:

i wouldn't mind havin a stab at it as well... oke:

 

[Bowtie]

I cant be a first edition 066 because they didnt have a decompression valve, I think. At any rate, that was a good deal, even if it needs a complete rebuild.


Check the bearings carefully after that kind of piston trauma. A vac pressure test is also in order.

 

[parrisw]

I cant be a first edition 066 because they didnt have a decompression valve, I think.

Yup, I had an old 066, it had no comp release. The thing was sure a good runner stock.

 

[Bowtie]

Is that a red light to boot!!!!!!!!!!!!!!

!

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

 

[Brmorgan]

I cant be a first edition 066 because they didnt have a decompression valve, I think. At any rate, that was a good deal, even if it needs a complete rebuild.


Check the bearings carefully after that kind of piston trauma. A vac pressure test is also in order.

Yeah, bearings and seals are on my list as well. If it's worth doing it's worth doing right, and it won't be that much extra work. Got a number for aftermarket ***/NTN/etc bearings for them, or is it OEM only on these?

 

[Stihl088stock]

You are 1 lucky guy...!

 

[Bowtie]

Yeah, bearings and seals are on my list as well. If it's worth doing it's worth doing right, and it won't be that much extra work. Got a number for aftermarket ***/NTN/etc bearings for them, or is it OEM only on these?

The flywheel side you can get from a local bearing shop (c3 clearance bearing). The clutch side is oem only.

 

[056kid]

Maybe the piston failed from heat. getting shut off alot just after heavy loads...

 

[AUSSIE1]

Yeah, bearings and seals are on my list as well. If it's worth doing it's worth doing right, and it won't be that much extra work. Got a number for aftermarket ***/NTN/etc bearings for them, or is it OEM only on these?

Brad all bearings are aftermarket anyway.
As long as the specs are the same you'll be right.

 

[Bowtie]

Brad all bearings are aftermarket anyway.
As long as the specs are the same you'll be right.

Where can you get the clutch side bearing aftermarket?

 

[Brmorgan]

Maybe the piston failed from heat. getting shut off alot just after heavy loads...

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.

 

[Brmorgan]

Brad all bearings are aftermarket anyway.
As long as the specs are the same you'll be right.

Well I know they're made by aftermarket suppliers, but whether or not they're reasonably common sizes that a bearing shop in a town of 15,000 can get is another matter. I've had decent luck with the two in town before though.

 

[ironman_gq]

When did they start putting intellicarbs on the saws. I thought those were relatively new.