066 Just stops. What gives???

[manual]

Thanks for all the great help. My delima is I bought it used off of ebay. A person runs the risk when they do that and have to weight out the odds based upon the sellers feedback and what type of auctions they normally run. I felt pretty safe with this seller and I pulled the trigger. I may have gotten burned, but if I did, it would be the first time I have on ebay.

Tonight, I'm going to:
1. take the muffler off and check the piston.
2. Pull the plug and check it out.
3. I'll try and adjust the high speed mixture.
4. change the mix from 50:1 to closer to 32:1.

If I don't get it to a point I feel confortable, I'll be at the saw shop at lunch tomorrow.

Welcome to the site as you can see their are a lot of people here that can help you. Like for instance if you were to say that you bought the saw off ebay in the first place, They would not think that you bought it from a dealer.
Yes it would be a good idea to take the muffler off and look at the cylinder.
there is a good reason why people sell saws on Ebay most times to get a new saw because there old saw is worn out. win some lose some.
Good luck with your saw.

 

[GPH85]

I would just like to add in a couple of comments if that is OK

First off, adjusting carbs on 2 cycles isn't easy although it can be picked up fairly quickly, but learning how to really get it "tuned" in takes time... When turning in the jets, never force them, just ease them in till they stop, then start backing out... If you force them, it may possibly ruin the jet seats or jets themselves = not good / new seats maybe even new carb... Best way to adjust (H) or your high jet is under load. Set it in a log or piece of wood and turn out or in accordingly until you hear max rpm's. If you wish, you can then "richen" it up slightly by backing the jet back out...

Second off, 2 cycles absolutely can't 4 cycle. Drop rpm's yes, but not 4 cycle...

Third off, if it's only running for this few of minutes and getting this hot tells me that you have some serious buildup of junk in the cooling system somewhere...

Forth, if it's getting hot, dying, then you have to wait for it to cool off before it will crank again, go ahead and get yourself a new coil. You can verify this to be your problem by pulling the plug right after it dies to see if there is any spark... Look for a nice thick bright "blue" spark, not a splindly "needle" looking yellow spark. If spark is good and blue, look for any fuel "breathing" problems as stated by Deuce32s... Ussually a saw won't drop slowly in rpm's if a coil is bad, it will either start missing durring idle, then just die or it will just die all together. If rpm's are dropping slowly, saw is running hot = may possibly be fuel leaning out durring operation from plugged breather on fuel cap...

You may be able to just replace your coil and go from there "after you clean out any air flow restrictions" if your spark doesn't look good or your fuel cap if spark is good...

Well, just some thoughts on the subject
Greg

 

[GPH85]

I forgot to mention that you can verify fuel cap breather being stopped up by running the saw with the cap partially loose or remove it after the saw dies, then choke saw several pulls to see if it fires again... May not even need to choke it, may just need to remove cap, reinstall, then see if it will start...

 

[Lakeside53]

The question has been raised and asked before about 2 stroke performance, they're either flat out or at idle and not designed to perform at half throttle .... that's from the very saw guys themselves, do some searches.

No one is taking about 1/2 throttle or anything, but full throttle. You are confusing this with the partial power jetting on the carb. Open the throttle full, and only the main jet has material influence.

You're assuming that the engine is capable 100% power for a full tank of gas and can cool that power... It's not designed that way... You need to derate the engine to stay within a reasonable thermal envelope. Richening up the mixture derates the saw - and the throttle is wide open. If you don't do this, the lifetime of the engine is compromised.

And Stihl does not "promote" or even suggest their saws for milling... at least not in the USA where EPA etc mandates a lean engine.

 

[Ekka]

Go to this site and read, there's also a couple of wav soundtracks to let you know what to listen for when adjusting the saw.

Reference is made as follows "NOTE: If you do not have a tachometer, set the RPM level so that the saw "four cycles" or "blubbers" at wide open throttle. Do not attempt to set at maximum RPM levels without a tachometer. Setting the adjustment slightly rich will diminish performance, but reduce the possibility of damage to the saw engine."

You may want them to change their terminolgy if you are unhappy about the term "4 cycling".

Source: http://www.madsens1.com/sawtune.htm

Oh, I have also sent an email to Stihl asking which saw they'd recommend for portable milling.

 

[Southern Boy]

Well, I checked the spark plug and it seemed fine. The gap was right at spec (0.5mm). I pulled the crank case off and cleaned the fins. I also pulled the muffler off and wasn't too happy.

I looked at the piston and it looks scored to me. The cylinder wall on the back side looks pretty clean, but the piston and rings have vertial lines (grooves) etched into them.:jawdrop: They are not nice and smooth like I would expect them to be. I find no evidence of metal shavings in the muffler or evidence on the spark plug. Could this piston have been changed out at some time? It seems like I have gotten burnt for the first time on ebay. First time in almost 70 purchases. Byer beware.

Can someone point me to a good thread on how to replace the piston and overhaul it correctly?

 

[Ekka]

Well, my hunch was a lean running saw with piston damage.

Could also have been caused by not putting the 2 stroke mix in the fuel (many a saw damaged due to that).

The saw guys will look after you.

Do some searches on ms660 and 066 etc.

Are you certain is was like that when you bought it? That's the only problem, the seller would claim "it was fine when it left here, who knows what he's done to it."

Ebay worries me, you have to be there physically and pull the bugger apart on a 2nd hand saw, or buy it from some-one who sells a few of them and is a saw builder etc.

 

[Deuce32s]

Check the compression on the saw. I just went through the same thing with my Partner. The piston and cylinder are scared but the compression is still good enough for the saw to last a while. I pulled the top end apart and cleaned the piston and cylinder up with some emery cloth. I know it isn't as good as new but it still has plenty of power to cut with its 16 inch bar. The saw that you have is probably easier to get parts for than mine so you could also make it better than I did mine. There isn't much to taking them apart. This was my first time and it was a piece of cake.

 

[Canyon Angler]

32:1 = more oil, less gas per unit volume. If your saw/carb is adjusted for 40:1 and then runs 32:1, it is now running the saw leaner. Oil lubricates, the incoming/fresh charge of fuel "cools" the saw, and the rings transfer the heat to the cylinder walls for removal. Less fuel makes the saw hot (lean), the hot saw then eventually flashes the oil that lubricates the rings, the hot rings become hotter due to increased friction as there is no oil, the rings and piston expand due to increased heat, piston melts, saw stops.

OK, I'm not a saw mechanic, and I won't pretend to know anywhere near what ya'll know about saws and saw motors, and I don't mean to hijack the thread, but I've been hearing this and it's just really hard for me to believe.

Let's look at the numbers:

The percentage of gasoline (by volume) in a given charge of 32:1 premix is about 97%.

(32/33 = 97%)

The percentage of gasoline (by volume) in a given charge of 50:1 premix is about 98%.

(50/51 = 98%)

That means that if a hypothetical single charge of premix has a volume of 10 cc, then:

in 32:1 premix there will be 9.7 cc of gasoline, and
in 50:1 premix there will be 9.8 cc of gasoline.

That means the 32:1 premix contains about 1% less gasoline per charge than the 50:1 premix.

Given the fact that most of the gasoline in a 2-stroke motor goes through the motor unburned anyway, I find it hard to believe that the motor will sense a 1% difference in the richness/leanness of a charge.

Again, I'm not a mechanic, but the numbers don't lie, either.

Can someone help me understand? :help:

 

[Southern Boy]

I don't know what the saw went through before I got it, but I DO know that I was feeding it a oil(stihl)/gas mix of 50:1. The saw never really was forced to go flat out for long durations. My homemade milling jig still needs a little tweaking, thus I just improvised with the Lumber Maker.

Here are some pics of what I found.

Ye 'ol spark plug. Checked gap and all was good.

This thing finned me.:biggrinbounce2: I cleaned these up good.

Breather with a headband.

The ugly part peaking up at me.
piston

piston

piston

Back of the cylinder wall. Not nearly as bad as the piston

I'm going to get the compression checked. If it doesn't cut the mustard, I'll replace the whole top end of it. Can someone point me to a good place to buy parts? What can I expect to pay for a piston head and new top end? Any manuf. I need to stay away from?

Anyone know anything about this rebuild kit or seller??? http://cgi.ebay.com/Cylinder-piston-kit-Stihl-066-MS-660-jug-NEW_W0QQitemZ230033302175QQihZ013QQcategoryZ85915QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Thank you guys sooooooo much for all your help and advice. There have been a lot of great discussion that has helped me understand chainsaws more and small engines in general. But Ekka, thanks for your respectful comments and advice. You have been especially a great help!!!

Kris

 

[aggiewoodbutchr]

OUCH. Looks like my 084 after a similar unfortunate event. Mine required a new piston but he cylinder was cleaned up with a hone.

 

[5555555]

You don't need to check the compression. That piston is toast. Great pictures by the way. It's hard to get good pictures of a piston.

Jim

 

[THALL10326]

I don't know what the saw went through before I got it, but I DO know that I was feeding it a oil(stihl)/gas mix of 50:1. The saw never really was forced to go flat out for long durations. My homemade milling jig still needs a little tweaking, thus I just improvised with the Lumber Maker.

Here are some pics of what I found.

Ye 'ol spark plug. Checked gap and all was good.

This thing finned me.:biggrinbounce2: I cleaned these up good.

Breather with a headband.

The ugly part peaking up at me.
piston

piston

piston

Back of the cylinder wall. Not nearly as bad as the piston

I'm going to get the compression checked. If it doesn't cut the mustard, I'll replace the whole top end of it. Can someone point me to a good place to buy parts? What can I expect to pay for a piston head and new top end? Any manuf. I need to stay away from?

Anyone know anything about this rebuild kit or seller??? http://cgi.ebay.com/Cylinder-piston-kit-Stihl-066-MS-660-jug-NEW_W0QQitemZ230033302175QQihZ013QQcategoryZ85915QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Thank you guys sooooooo much for all your help and advice. There have been a lot of great discussion that has helped me understand chainsaws more and small engines in general. But Ekka, thanks for your respectful comments and advice. You have been especially a great help!!!

Kris

Welp now you see how hot it really got, not good. That saw overheated bigtime, thats a bad score there. Most likely that saw wasn't tuned for milling, (rpms way to high) and she fried. Some will argue blah blah its the saw but fact is that would happen to any saw over reving in milling. Milling requires a different set up than blocking, much different set up. Get a jug and piston and throw it back together, the saw is worth repairing. If your going to use it again for milling break in the engine first and then tune it for milling....

 

[GPH85]

I agree with Thall and others This one's junk... But remember you still need to fix your dying and other issues... Check that fuel cap = this thing ran really lean because of something... Got so hot it turned the piston rings blue = not good at all... You didn't do anything wrong here, as far as I can tell from what you have explained and said, it's just something lead up to this happening. Could have even happened cutting firewood for all you know

In order for a 2 cycle engine to 4 cycle it would have to miss every other revolution = not possible!!! I don't care how some one explained their methods, because humans are more than capable of error...

Second off, in order for a engine to 4 cycle it would have to have individual strokes (intake, compression, power, exhaust) = fires every other revolution... A 2 stroke is called a 2 stroke or 2 cycle for a reason, because it fires every revolution, not every other!!!

Yes you adjust a carb till it may start to "blubber" or "gargle", but not till it "4 cycles". Like I said, I only use this method for rough tuning, fine tune in a piece of wood under load... I've used this method for years with many great results. Never had one burn up from running lean either.

 

[Lakeside53]

That piston is toast - plain overheated and melted. Once the exhaust side lip of the piston starts to melt, it snowballs into what you see very quickly. Most likely a combination of poor cooling (dirty fins and air path), lack of lubrication (50:1 mix) and excessive power for extended periods. Whether this happened before you got the saw or due to your work is hard to say. The prior owner could have easily put in a new plug after wrecking the saw, and you just didn't know.

The plug shows the mixture was correct for ordinary work, but not for the 100% duty cycle required with milling. My plugs are quite black when milling, as they should be at an excessively rich mixture.

For milling, I'd stay away from any aftermarket pistons and cylinders. Stihl has the 066 set real close to the edge for normal work, and milling might just take it over. They've modified the piston a few time to increase life. The downside is you're looking at $330 verses whatever for the aftermarket set.

You might get away with just a piston, but you can't tell until the bore is cleaned up and honed. The inlet side looks pretty bad.. usually it's untouched, so the exhaust side may be bad.

BTW, your air filter needs some attention...

 

[Lakeside53]

I agree with Thall and others This one's junk... But remember you still need to fix your dying and other issues... Check that fuel cap = this thing ran really lean because of something... Got so hot it turned the piston rings blue = not good at all... You didn't do anything wrong here, as far as I can tell from what you have explained and said, it's just something lead up to this happening. Could have even happened cutting firewood for all you know

In order for a 2 cycle engine to 4 cycle it would have to miss every other revolution = not possible!!! I don't care how some one explained their methods, because humans are more than capable of error...

Second off, in order for a engine to 4 cycle it would have to have individual strokes (intake, compression, power, exhaust) = fires every other revolution... A 2 stroke is called a 2 stroke or 2 cycle for a reason, because it fires every revolution, not every other!!!

Yes you adjust a carb till it may start to "blubber" or "gargle", but not till it "4 cycles". Like I said, I only use this method for rough tuning, fine tune in a piece of wood under load... I've used this method for years with many great results. Never had one burn up from running lean either.

I don't think anyone (even Ekka ) is trying to say it actually 4-cycles... just the name for the sound...

Tuning for the "blubber" is fine for ordinary work (works for me), but for milling you need to adjust it even further into the rich zone to detune the engine for a lower output.

The fuel cap has nothing to do with venting on an 066 - the tank vent is separate.

 

[Ekka]

Wow & ouch.

Really nice pics, bravo. 66's here cost $2000, how much did you pay for that one?

Now, I emailed Stihl. Then the Germans emailed Australia office and got a guy to answer my question.

My question was, what saw do you recommend I buy to use for portable milling?


They then responded with what type of mill, an Alaskan or Mini mill?

I told them Alaskan

This is the reply ... Hi Eric if you are going to go for the Alaskan mill I would say go for the MS880.

Regards Dale Rinaldi
Technical Advisor
Stihl Aust Pty Ltd
Knoxfield Vic 3180.

So, I stand by my earlier comments, but I also acknowledge that things could be different here due to emission control standards etc.

I run all my saws at 32:1 mix and I never use the higher octane unleaded, I think normal unleaded is 92 octane, then there's the next grade up called 95 and then there's a premium grade 98 octane.

Now I only ever use the 92 stuff, do you think (saw guys) that the higher octane fuels are good/bad for your saw?

Also, I dont believe that cylinders can be honed.

And I hear you shouldn't run in your new saw (piston & jug) on synthetic 2 stroke mix like Stihl ... you are better off to run it in on the old mineral oil (dino oil) mix at 25:1

 

[CaseyForrest]

Octane ratings here go 87, 89, 93. Its either Shell or Sunoco that has 94. I use 93.

 

[Ekka]

Darn, you guys measure it different to us.

Ours is called RON and you guys use MON

http://en.wikipedia.org/wiki/Octane_rating

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-95 (regular) in Europe.

But then to confuse matters a little more, there's PON. Which is Pump Octane Number used in USA and it's an average of the MON and RON numbers!

http://www.btinternet.com/~madmole/Reference/RONMONPON.html

There's also a chart in the above link for converting them.

 

[Lakeside53]

Also, I dont believe that cylinders can be honed.

And I hear you shouldn't run in your new saw (piston & jug) on synthetic 2 stroke mix like Stihl ... you are better off to run it in on the old mineral oil (dino oil) mix at 25:1

Officially Nikersil or Chromed cylinders shouldn't be honed, but, everyone does it with very good results. The honing is only to remove aluminum deposits that won't come off with acid, and to deglase. Virtually no material is removed from the bore plating as it's so incredibly hard. I once put a hone (lubricated with normal cutting oil) in a ruined 026 cylinder for about 30 minutes to see if I could cut though the nikersil - not! New cylinders of both Nikersil and chrome are honed to a specific surface finish and size at the factory using a diamond hone. The old chrome was just plated on a pre-honed surface, but no longer. We're just "touching up" the factory hone...

I specifically (and officially as a Dealer) asked Stihl if the we could use their new synthetic oil during the break-in period for new saws - the response was "absolutely". I has heard the same info about not using it over the years and Stihl says that is is just one of the many myths that floats around. The stihl cylinder has a very fine diamond hone finish from the factory that is almost untouched for hundreds of hours (you can still see the fine cross hatch). The rings wear, but the bore wears very little.