Would you keep this piston?

[mheim1]

Looking for opinions:
Stihl 066, personal saw (might use it twice a year just to cut the big logs), 135psi compression, cylinder looks good.
I have it apart already just for a cleaning and rubber replacement and wondering if I should just put some new rings on it, or a Meteor piston or just put it back together?
Appreciate thoughts.
Thanks.

View attachment 214265
View attachment 214266

And apparently, I haven't posted pictures in a while, as I can't seem to figure out where that little 'mountain looking thing' went. Sorry about that.

 

[50blues]

pistons are cheap, why take the chance. go new.

 

[WidowMaker]

I'd reuse it with out a second thought...but thats just me...

 

[pioneerguy600]

In my own saw,for my own use I would use that piston without even blinking, clean it up and install new rings, it will give years of service.

 

[Motorsen]

Give it new rings! Maybe a piston.

But it look like the saw have eaten dust due to the scratches on the piston. Maybe thats what you are rectifying with the "rubber replacement"?
If your comp gauge reads true numbers the compression is a bit on the low side. Maybe both ring and piston. Rings for sure.

Motorsen

 

[Bowtie]

But it look like the saw have eaten dust due to the scratches on the piston. Maybe thats what you are rectifying with the "rubber replacement"?
If your comp gauge reads true numbers the compression is a bit on the low side. Maybe both ring and piston. Rings for sure.

Motorsen

I have messed with saws that were pretty new or fresh that had marks like that. Doesnt mean they are screwed up. I would check skirt clearances, compression, and if they check out and the saw runs well, use it.

 

[pops21]

Yep I have saw brand new saws posted on arborist site with those scratch marks on the piston. Nothing really wrong as long as compression is still good. Buttttt 135 is pretty low.

If it were me I would just stick a new set of rings in it.

 

[jus2fat]

Just Rings..!!!

J2F

 

[jbighump]

throw some caber rings in it and also maybe a airfilter good to go

 

[Terry Syd]

I learned a long time ago never to throw away a piston that could be used for testing. Check the clearances, if they are good then go with new rings. If it is out of clearance, then save it to try some mods.

You can trim the edge next to the exhaust port to see what a few more degrees of blowdown will do for the power.

You can trim the intake skirt to see what a few more degrees of intake will do for the power.

You can trim the edge next to the transfers to see what a few more degrees will do to the power.

And when you are done playing, you can always go back to the stock piston.

New pistons are a lot cheaper than new jugs.

 

[mheim1]

Thanks guys; just what I thought as well.
New rings and maybe even a little less squish.

 

[Dan_IN_MN]

I have instructions on how to embed pics in my sig...

IMO....I'd use the piston....how was the saw running?

 

[fearofpavement]

piston looks fine to me. New rings will probably bring the compression up.

 

[Dan Forsh]

Apart from the scratches, that piston shows no signs of real wear. If the compression reading is accurate I would go with new rings anyway, but I would wonder why the scratches? Has your maintenance been less than ideal?

 

[Opihi59]

Looking for opinions:
Stihl 066, personal saw (might use it twice a year just to cut the big logs), 135psi compression, cylinder looks good.
I have it apart already just for a cleaning and rubber replacement and wondering if I should just put some new rings on it, or a Meteor piston or just put it back together?
Appreciate thoughts.
Thanks.

View attachment 214265
View attachment 214266

And apparently, I haven't posted pictures in a while, as I can't seem to figure out where that little 'mountain looking thing' went. Sorry about that.

I'd run that piston, just put on new rings. I"m going to guess your cylinder looks pristine. Recently I've put some pistons back into saws with similar marks and get great compression with new rings. Caveat is that I do not consider myself to be "Mr Definitive Chainsaw Authority." What I've done has worked fine.

If you do go for a new piston, find a nice sawdust pile and plant the old one there, moisten regularly with 2 stroke oil, maybe will grow another Stihl 066 from it eventually.

 

[Jacob J.]

Apart from the scratches, that piston shows no signs of real wear. If the compression reading is accurate I would go with new rings anyway, but I would wonder why the scratches? Has your maintenance been less than ideal?

Looks fine to me as well but the saw has obviously gotten some hard use. Those scratches are either caused by pieces of carbon letting loose and getting between
the piston skirt and cylinder wall, or the saw has been ingesting debris. Sometimes in a new saw, there'll be slight burrs left around the port edges which cause scratching
that the guys are talking about above.

 

[pioneerguy600]

Looks fine to me as well but the saw has obviously gotten some hard use. Those scratches are either caused by pieces of carbon letting loose and getting between
the piston skirt and cylinder wall, or the saw has been ingesting debris. Sometimes in a new saw, there'll be slight burrs left around the port edges which cause scratching
that the guys are talking about above.

Jacob,..I have a brand new 660 cylinder that has ridges left on the bottom of the intake port, where it should have been chamfered, that would scratch up a piston as bad or worse than the piston in this post.

 

[mheim1]

I have instructions on how to embed pics in my sig...

IMO....I'd use the piston....how was the saw running?

Have to bookmark those instructions; thanks.
The saw was running (well, it started) when I got it; never used it.
It was pretty dirty and some of the hoses/intake boot showed some age, so I decided to tear it down. My old 066 only had 135 psi and ran great.

 

[wigglesworth]

Them black specks imbedded debri?

 

[Jacob J.]

Jacob,..I have a brand new 660 cylinder that has ridges left on the bottom of the intake port, where it should have been chamfered, that would scratch up a piston as bad or worse than the piston in this post.

Yeah I've seen that too. We had a run of brand new 460s back around 2001 that were so bad we were having to take new saws off the shelf, pop the jugs,
and chamfer the intake and the bottom of the transfers by hand. Stihl reimbursed us for the labor under warranty.

Them black specks imbedded debris?

That or embedded carbon from detonation.