084 and 066 top end

[00juice]

I own an 084 and 066 that I've used for milling pretty much exclusively, although I've done not all that much milling. (The 084 was ported, 066 stock) A couple years ago, while in the middle of a 48" oak, I had the 084 stop running. Didn't think much about it, and grabbed the 066 to finish the job. A few minutes later, it also stopped running. Took the saws to local stihl dealer. They told me both saws needed new top ends. Had the 084 jug replaced with an old oem and new piston. Didn't have the $ to fix the 066, so it continues to sit. Saw the 066 sitting in garage the other day, and it Got me thinking about went wrong that day. New high test gas that morning from a very small off the path gas station, mixed with mobil1 2t at 40:1. Could bad fuel have caused the damage? Here's some pics of the cylinder/ piston from 084. Trying to decide what to do with 066.

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[lewis16]

I know this isn't relevant, but that probably won't buff out. Looks like something broke off and just went to town on everything. No debris in the crankcase? Needle from a bearing missing?

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[00juice]

I know this isn't relevant, but that probably won't buff out. Looks like something broke off and just went to town on everything. No debris in the crankcase? Needle from a bearing missing?

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Honestly don't know if any debris was in crankcase. All this happened a few years ago. Had the 084 repaired and asked for cylinder piston back at the time. Never looked at the cylinder/ piston until today when I started contemplating the fate of the 066.


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[00juice]

Also curious of any bodies thoughts on the port work as well. In reality, that top end probably didn't have more than 15 hours on it.


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[lewis16]

Well if I was you I'd take the exhaust off the 066 and see if there is any damage in there. If there is, will be a good idea to put a big bore kit on there. Providing the bearings and seals are good.

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[pioneerguy600]

It appears to me that there were an awful lot of sharp edges left on the port work. Something appears to have broken loose in there, bearing cages does damage like that most often.

 

[00juice]

Well if I was you I'd take the exhaust off the 066 and see if there is any damage in there. If there is, will be a good idea to put a big bore kit on there. Providing the bearings and seals are good.

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Looking in the 066, I can see some scoring on the piston, but not the cylinder. Although, cylinder damage that would match the piston is on the side of the cylinder I can't see.

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[lewis16]

Piston looks amazing, Machining marks are still there and it doesn't look worn.

My 576xp cut out randomly the other week, turns out the cylinder head bolts had worked loose, tightened them up and it was sorted.

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[00juice]

Piston looks amazing, Machining marks are still there and it doesn't look worn.

My 576xp cut out randomly the other week, turns out the cylinder head bolts had worked loose, tightened them up and it was sorted.

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[00juice]

Hard to see in pic, but scoring on left side.

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[lewis16]

Oh I didn't even notice that. If it has held the ring in that would stop it. Has it got compression?

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[pioneerguy600]

The 066 jug needs to come off.

 

[00juice]

I have never pulled a jug. Any special procedure?


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[lewis16]

Muffler off, carb and intake boot off, impulse line off then it is as simple as removing the 4 cylinder head bolts and then pulling it off.

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[00juice]

I'll pull it tomorrow


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[nstueve]

I don't disagree that the porting could have been the 084's demise but when both saws died the same day, under the same gas... That makes me suspicious and I would suspect you probably had bad fuel too. I usually mix and shake my 2 stroke cans and pour some into a glass jar to see if water separates within a day or two before I use it. Can't be too careful...

Pics looks like a classic water in the fuel problem to me. Water causes detonation which will leave pitting and erosion in the cylinder squish area and piston top. I had my neighbors 395xp in a couple months back, and he didn't know why the saw wouldn't run... I checked the compression and it was a little low. I checked the cylinder he had the same round pitting in the top of the cylinder and on the piston as well as eroded piston sides like yours. I cleaned the cylinder, put in a meteor slug, and changed the fuel filter and fuel line. Solved his problem and he hasn't had any problems since.

Stihl sells these little vials to check your fuel. 2storke mix binds with only gas so you can see all the water in the bottom. Glass jar or water bottle does the same thing...

Also keep in mind that gas isn't the only problem that can cause detonation. Timing being way far off could cause it too.

 

[00juice]

Thanks for the info. I'm gonna start checking fuel like you suggested. What are the stihl vials called?


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[nstueve]

not sure.

 

[asauer]

How long does it take to separate out nicely like that? I see you say you wait a few days.

 

[wde_1978]

I have never pulled a jug. Any special procedure?
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Muffler off, carb and intake boot off, impulse line off then it is as simple as removing the 4 cylinder head bolts and then pulling it off.
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... AND clean off all the gunk surrounding the cylinder base and being stuck in the cylinder fins BEFORE You pull the jug.

You do not want that stuff to fall into the crank case.

Compressor does a good job, take off the covers but leave the carb, air filter, plug and muffler on so nothing gets into the cylinder.