Stihl 066 Logosol woes

[Log Hogger]

I just burned up the rings/cylinder/piston on my 066 while running it on a Logosol. The exhaust side of the piston is deeply scored and the rings have melted into the grooves on that side. On the intake side, everything looks great, with a mirror finish and no signs of overheating. My guess is that because the muffler is right up against the tree while ripping, maybe it got clogged and overheated? This saw has seen very little use so I must be doing something wrong for it to burn up a piston.

I've already found lots of great info on this forum, but I still have a few questions.

1. Where is a good source for a new piston-cylinder assembly? I checked a Stihl dealer nearby and was quoted $261.05, but online I can't fund anyplace that lists the assembly for an 066.

2. How do I prevent this from happening again? Should I try to get more distance between the saw and the log (not sure if this is possible, since I'm not the one doing the ripping). Would a "dual-port" muffler help, or could I modify the stock muffler in some way?

Thanks for any help! Also, any tips on replacing the cylinder/piston assembly are welcome. I've rebuilt 4 cycle lawn mower engines but never any 2 strokes.

 

[pinus]

Probably carb is set to lean mix and/or there is little oil in the fuel. If tere is more than some 2" (may be even less) between log and muffler, the log cant block exhaust, IMO

 

[Log Hogger]

Ok. It's my father's saw but I do the maintenance for it along with an 028 wood boss that I use myself. Of course he swears up and down that he only runs perfectly mixed 50:1 fuel/oil mix, as would anyone I suppose - that's one expensive mistake. As far as the carb settings, they are the same as new, my father wouldn't touch those and like I said, the saw has seen very little use.

Why would too little oil only damage the exhaust side of the piston? Is it because that's just where the most heat is?

Also, I forgot to ask in the original post, does anyone know where I can find some exploded view parts diagrams for this saw? I'm not experienced in working on these saws, so some instructions would be nice. The Stihl dealer had some, but they had no copy machine, so all I could do was look (no photographic memory).

 

[MacDaddy]

I would cut out the baffle in the muffler put a dual port front And run klotz mix oil @32/1 also remember that the saw has to have a blubber on top or it is to lean and you will burn the saw up again Also call Dean (klickitatsacket) he will get you a top end cheaper than the price you have listed

 

[DanManofStihl]

I would put amsoil or mobil one mix in the next saw/kit and run it at 32 to 1. I sent my 066 muffler to walkers and had them modifie it. My saw runs alot cooler and it has more power you have to adjust the high side and make it riocher or you will burn it up again though. I think the 50 to 1 stihl mix is way to lean for milling.

 

[rmihalek]

What MacDaddy meant about "blubber on top" was not to go get some whale fat and grease up the piston. He means to start the saw and let her warm up, maybe do a couple cuts. Then, with the saw out of the wood, just sitting on the ground, get a screw driver and put it on the H screw on the carb (high speed jet screw) and then run the saw at full throttle. After a second or so, start backing the H screw out slowly until you hear the exhaust note start to break up a bit (some folks call this "four stroking"). Let off the throttle and let her cool down a bit. Then, turn the screw in a little (1/8th or 1/4 turn), open the throttle to full and see if you still hear the burbling. If so, try another 1/4 turn in, maybe the burbling will go away and the engine will just scream. That's too lean. Back the screw out again.

You should do this process several times once you get the new top end put in as the rings seat in the cylinder. Why? The compression will go up and the engine will need more fuel (a good thing!) so you'll need to open the H jet so you don't fry another top end
.

 

[timberwolf]

I echo the same ideas, synthetic, 32:1. Castor oils anti-sieze properties shine in heavy duity-cycle applications if the smell does not bug you. Watch not to let the saw run out of gas as this sends it lean each time followed by a stopage without a cool down.

Warm the saw up and cooling down by ideling a minute or so after a long cut, and avoid milling in hot weather.

Good luch with the jug

open that muffler up.

 

[rbtree]

timberwolf, are you referring to Maxima 927? Some builder/ racers used to run it but quit because it caused some problems in a chain saw. I forget the reason. You might try a search of the archives here... about 2003-2004.

 

[MacDaddy]

What MacDaddy meant about "blubber on top" was not to go get some whale fat and grease up the piston.
.

No I mean find a eskimo and steal some from him or that saw will always run lean HAHAHAHAHAHAHAHA

 

[MacDaddy]

Also if you adjust the high side correctly you will have more torque than if you were to lean it out some to get the rpm out of her after a good long cut the screan in the muffler should be brown not black or white so you can adjust to that if that will help you

 

[timberwolf]

RBtree, I can't seem to find aything, some opinions on castor as causing carboning and sticking rings... I don't think that is the case with the 927. They must add something or use processed castor as the problem is not evident with the 927.

In my own experience the 927 has left no deposits with a good amount of use. In one saw I have piston crown and exhaust was polished to a mirror finish, recently took it apart after several months of use and all that was on the piston and port was a film that looked like corn syrup, a wipe with a paper towl and it looked as it did when I put it together.

I think Some of Gorden Jennings writings and experiments touched on the use of castor oil for heavy duity use and in high mix ratios, overall it was suportive but maybe not conclusive that the castor worked well for that aplication, and that would have been in the 70's long befor the anti fouling advances of 927 or other such oils

 

[Chris J.]

Also, I forgot to ask in the original post, does anyone know where I can find some exploded view parts diagrams for this saw?

Thompson1600 here at AS has Stihl info at his site GiftsOfWood. If you don't find it there, let me know & I'll see what I can find on my Stihl disk. The disk also has detailed repair instructions; I'm not sure about GiftsOfWood.

Chris J.

 

[klickitatsacket]

I am putting an order together now for a piston and cylinder order. Stihl OEM 066 is $170 shipped to you.

 

[Log Hogger]

Many thanks, you guys are all a fountain of knowledge. I think I learned more about my problem in this thread than in talking to the service guys at two different Stihl dealers (although in fairness, they wanted to fix my saw, not help me fix it myself). Knot Whole, Thompson had both an IPL and a service manual for the 066, I'm downloading 'em now. Dean, check your PM, I'll be putting in an order today if possible.

I'll keep you all updated on this project so you know when it's back up and running!