Run it or replace it, Stihl 066

[Firstyear50]

Starting to clean up potentially the dirtiest saw I've ever seen. It's an 066 that I think lived in the back of a truck for a while. Needless to say, the intake has swallowed some grit over the years. As a result, there's some slight scoring on the intake side, and a bit of wear on the exhaust side. Would you guys replace the piston, or run it as is? Compression is over 150, so I'm tempted just to run it.
Intake side:

Exhaust side, notice how there are some original machine marks left but most is worn away:


Lastly, I can see some paint chipping away inside the crank case. I'm not going to split this one as the seals and bearings are fine, any pointers on how to get the chips cleaned up?

 

[lone wolf]

Overhaul it . Clean the cylinder up install new, piston and rings , crank seals, base gasket ,impulse line and fuel line.

 

[JonCraig]

It's toast. I'll pay shipping ifn you want to be rid of that boat anchor.

 

[Frogfarmer]

Replace the piston. I'd do everything but that might not be feasible for you.

 

[Firstyear50]

I guess I expected that. I know I should replace the piston. Im curious though, if compression is fine what is the harm in running a slightly scored piston?

 

[lone wolf]

I guess I expected that. I know I should replace the piston. Im curious though, if compression is fine what is the harm in running a slightly scored piston?

Compression is decent it will run go try it and see if you are satisfied. If not well you know what to do.

 

[JonCraig]

You'll forever wonder how much stronger it would run with 3 pounds better compression.

 

[Frogfarmer]

You could run the piston but it's already down and showing signs of wear and tear. It is cheap insurance to replace the piston with a meteor or OEM on a work saw of this class.

 

[Firstyear50]

You'll forever wonder how much stronger it would run with 3 pounds better compression.

You know, you're not wrong about this...
I guess I'll just replace it. For 60 bucks you guys are right, it's cheap piece of mind.

 

[CascadeHusky]

I guess I expected that. I know I should replace the piston. Im curious though, if compression is fine what is the harm in running a slightly scored piston?

No, there isn't a problem with running it as is, and it's not some thing you should do. It isn't your father's pacemaker, it's a scuffed piston on a used saw. 150 psi on a big saw isn't a problem. If it runs fine, great. If it runs good now and in a few dozen tanks it measures 130psi and isnt running as well, then you might want to replace it. You can change it now if you want, but please don't bc someone looked at a picture and guilted you with their OCD.

When people are telling you to replace a piston bc it's scratched, but aren't telling you how to get rid of paint chips that are soon to be floating in your case, beware.

 

[svk]

I'm not an expert but I agree with cascade.

Split the case and get rid of that problem paint. It's going to raise heck when it decides to come off.

 

[Big_Wood]

how much are you gonna cut with it? if it's a saw you have to rely on everyday i'd replace it for sure but then i'd likely do the bearings too. if your a firewood guy and just need a big saw for that odd big log once a year save your money. i have some tired saws and some fresh ones. i still run the tired ones but i got a fresh one nearby for when they do go. i'll rebuild a saw that died young but i don't rebuild saws that have insane hours. just go buy new at that point.

 

[JonCraig]

i don't rebuild saws that have insane hours. just go buy new at that point.

Nonsense! Where's the fun in NOT sourcing NLA parts for a saw I don't need? And spending way more money on it than I'll ever get back out of it?

That's crazy talk, man! You been talking to my wife?

 

[Firstyear50]

how much are you gonna cut with it? if it's a saw you have to rely on everyday i'd replace it for sure but then i'd likely do the bearings too. if your a firewood guy and just need a big saw for that odd big log once a year save your money. i have some tired saws and some fresh ones. i still run the tired ones but i got a fresh one nearby for when they do go. i'll rebuild a saw that died young but i don't rebuild saws that have insane hours. just go buy new at that point.

That's actually a good point, I picked this saw up mainly because the ol Jonserd 90 I used to handle the huge stuff finally gave out on me. I'm just a firewood guy, and cut around 50 cord a year. Most of this is easily handled by my 044, 036, or 261. There's really rarely a need for a saw of this size in the wood I cut, but when there is a need I'd like it to not give me trouble you know?

As for the chipping paint, I'm trying to avoid splitting the case if at ALL possible. Tomorrow I'm going to get after it with a small wire brush and a pick, I'll keep you guys posted. Thanks for all the replies.

 

[JonCraig]

That's what I would do for the paint. Chip off everything loose, rinse the crankcase w/ mix into a coffee filter until no debris comes out.

 

[Vtrombly]

I say run it as is myself the scoring isn't into the rings worse case scenario you hone it and rebuild it when the comp drops.

 

[Chainsaw Jim]

You can use a plastic dish scratcher scrubber to tuck in front of the balancer to clean the crankcase out. The balancer will drag it through there and it will knock the bubbled paint loose. Pull both seals to help rinsing it out since they should be replaced anyways.

That piston is toast. Yeah you can run it but that wear on the skirt bottom will allow it to rock enough to wear away faster than normal... until it hangs up and grenades.

 

[Mad Professor]

Paint chips and what will fall off under will come back to haunt you.

You should have cleaned things a bit more before pulling the jug, probably more than paint chips down there

 

[Firstyear50]

You can use a plastic dish scratcher scrubber to tuck in front of the balancer to clean the crankcase out. The balancer will drag it through there and it will knock the bubbled paint loose. Pull both seals to help rinsing it out since they should be replaced anyways.

That piston is toast. Yeah you can run it but that wear on the skirt bottom will allow it to rock enough to wear away faster than normal... until it hangs up and grenades.

Good idea on the dish scrubber, I'll give it a try. I really hate to pull the seals though, I have not had good luck in that area. I know it should be simple, but it still makes me nervous since they don't leak now.

As for the piston, I went ahead and ordered an oem replacement last night. Whether I wanted to or not, I think it was the smart choice.

 

[JonCraig]

Whether I wanted to or not, I think it was the smart choice.

Your cookie times, when 0.025/second faster, will appreciate it.