# Problems with Stihl 066m



## [email protected] (Apr 30, 2007)

I hoping you guys might be able to give me some direction on what to do with this saw. The saw is a stihl 066m. I was cutting up a downed tree and while sawing at near full rpms the saw locked up. Checked the fuel and there was oil in the gas. I let the saw cool down then i put some two cycle oil in the spark plug hole to lubricate the cylinder and hopefully reduce any damage. I turned the motor in reverse and freed the motor. I drained all the oil i cold out of the spark plug hole. The motor seems to turn fine now. But I can not get the engine to fire. I put a new plug in and checked to make sure it was firing. After trying to start the motor several times i pulled the plug out and you couldn't tell it has burnt anything. The saw is blowing fuel out the compression relief valve the the motor doesn't fire. I'm not really knowledgeable about the internal workings of these motors. It just doesn't make any sense to me. Is the motor fried, you think? Anything else i need to check? Any advice would be greatly appreciated.

David


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## sILlogger (Apr 30, 2007)

package it up and send it to me...ill give u a good price for it have u checked for spark? pull the plug out and with it plugged into the wire ground it out and pull it over to see if it sparks


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## ShoerFast (Apr 30, 2007)

Welcome to the site David

When you say it locked up,,,,, do you mean that it just quit? or locked up and would not turn over by the rope?

First place to look for engine damage is by pulling the muffler

It was mentioned how to check for spark.

But a better idea, just package that saw up, and I will top the offer by that other guy!


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## sILlogger (Apr 30, 2007)

dbarbee, your my neighbor, i live over in carbondale, IL. only 70 miles away. small world. are u a logger, or an occasional chainsaw user. is it a newer or older model 066? i hope u get it figured out. if it stopped suddenly, as in came to a screaching halt i would definitely pull the muffler and look at it. or send it to me, i'll send a check and get it out of your hair keep us posted on what u see as you get into it and u will get all the help u can handle. welcome to the site btw


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## [email protected] (May 1, 2007)

The saw does have spark. I have haven't pulled the muffler yet. Took a small peak through the spark plug hole, didn't see any shavings or anything. When i saw the saw locked up, the motor wouldn't turn. I had to turn the motor backwards by hand to free it up. Since it locked up the motor hasn't even tried to start. The saw was bought about 6 years ago or so. My main line of work is woodworking. I have a woodmizer sawmill and use the saw only for cutting logs to size. Really the saw never saw that much use. It had always run perfect, well, right up until it locked up. If the motor is unfixable, I was just trying to figure that out before taking it to somone who would charge $50 dollars for that news. If I do need a new motor does anyone know how much that would cost or a supplier? I appreciate all the offers to take it off my hands but if its cost effective to repair i would just assume give that a shot.


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## ShoerFast (May 1, 2007)

From the hip, 

You may find that your going to need a cylinder - piston, Baileys , a site sponsor has them for $120 - 








http://store.baileys-online.com/cgi-bin/baileys/5638?mv_session_id=68tBaw6t&product_sku=CK 066

They also offer a Big-Bore kit for that saw, but last I have heard is that it has been placed on the back burner.

Remove the front handle (4-screws) the top plastic, and the cylinder (4 Torex head screws) and your there. checking the crank rod and bearings, but if it just needs a top-end , it would be hard to spend an hour at it.

Mic the wrist-pin, if there the same (no excessive ware on the original,) use the original wrist-pin,,,,, a lot lighter.

Edit: should mention find the reason it siezed, crank seal, tore loos inlet boot, lean fuel delivery,,,,


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## sILlogger (May 1, 2007)

i agree with shoerfast on that one, find out what caused the lockup problem before throwing on a top end. keep us updated on what u find. good luck


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## [email protected] (May 1, 2007)

I saw that a recent bailey's catalog i have here at the house. Is this a repair that a layman could pull off or do I just need to take this to a professional? Done alot of maintenance but never overhauled a motor like this before. Thanks...


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## sILlogger (May 1, 2007)

if u can follow directions u can pull it off,4 torx bolts for the top cover, pull spark plug, loosen and remove intake boot from cylinder. take off 4 cylnder bolts out remove cylinder. pretty much the jist of it. if i was you i would buy the Wiha T27 torx wrench and the piston ring compressor from baileys while your at it, go to your nearest stihl dealer and get the $3 base gasket, skinnier of the 2,( i think .5mm.) put it on install new cylinder, minor carb adjustments. 

then there is always the concept of ship it off, pay 3-400 and have it woods ported AND get a new piston an cylinder, and have a bad azz saw that will be alot of fun!! which is what is going to happen with my 066 soon.


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## ShoerFast (May 1, 2007)

[email protected] said:


> I saw that a recent bailey's catalog i have here at the house. Is this a repair that a layman could pull off or do I just need to take this to a professional? Done alot of maintenance but never overhauled a motor like this before. Thanks...




Take it one step at a time,,,

It is really a straight forward replacement, once you find the reason it seized.

You may find out more once it is apart, but just plan on double checking/ replacing the fuel-line, filter, impulse hose, double check the inlet-boot and check the crank seals,,,,, or just plain replace them. Might as well OH the carb also. set the cylinder on a new gasket and your really covered. 
It's just me, but I don't like to toss parts at something in hope I fix something, knowing whet seized it would give you a lot of comfort!



Pay real close attention to how it runs at first, keeping it close to a good 4-cycle burble for a few tanks.

Something will happen while you run your first rebuild, there are no words for it, but you will know what I mean when it happens 

Push come to shove, there are sponsors here that would take that saw as a basket full of parts and send it back fixed or a hot-rod (modded / ported) saw, Dean at Washington Hot Saws is one of them.


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## [email protected] (May 1, 2007)

*Update with pic*

Heres what I found when I pulled the muffler.






You see how chewed up the piston is. The damage seems to be only the the muffler side of the motor? Assuming this is because of the heat on the exhaust side. The cylinder wall seems to be in great shape on the intake side. You can still see the milling marks in the cylinder walls. Wouldn't that lead you to believe heat was what caused the motor to seize, rather than mechanical reasons? If thats the case what would cause the motor to run so hard that it overheated? The only thing I could think of was lack of oil in the gas mix, but like I said I checked that. I'm pretty careful about that. I use the Stihl oil that has already been premeasured.

After seeing the damage I was going to go ahead pull the top of the motor off but i ran into a problem. How the h*ll you supposed to get those 4 torx screws out? :help:


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## sILlogger (May 1, 2007)

a long handles T27 torx, or the L-wrench that usually comes with a stihl weedeater, u could prolly to buy a T handle wrench at walmart or a hardware store, or baileys has them


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## ShoerFast (May 1, 2007)

The exhaust side is also the thrust side, the piston has more of a side load firing then dose the compression side or intake side.

Just from what your pix is showing, pull the jug and get a better look, if there is metal missing from the cylinder, it may be time for a new cylinder. 

A good picture from the inside and maybe it will be a little more clear on why it seized?

Dose this saw have a lot of hours on it?


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## [email protected] (May 1, 2007)

I would say they saw has less than 20 hours on it. Its used seasonally to cut logs to length for my sawmill. I don't use my sawmill commercially, just to provide me with lumber. This saw has never been used commercially. Maybe that is some of the problem, lack of use may have let a seal dry out. I stopped in and talked to a repair guy today and he explained a little about what you guys have been telling me. He said he thought it was definitely from an air leak. He told me that if I would get the parts to rebuild it he would put the kit in for approx $110. That was for labor on the cylinder kit and crank seals. Still debating. Would love to take top of the motor off to talk a look but those exaust side torx screws in an awful spot. Still haven't been able to get those out.


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## sILlogger (May 1, 2007)

if u have a long handles torx u can go down through the holes in the cylinder fins and get to the cylinder bolts. 20 Hours!!!! that sure isnt' very many........hummm.....do u clean the airfilter pretty often?? u might be surprised how salvageable a cylinder is, atleast i was when i started working on saws. a good honing will go a long way. u might be able to get by with a $50 cylinder, but still too early to tell


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## ShoerFast (May 1, 2007)

Should be able to pass the Torex all the way down from the top via holes in the cylinder fins?

If your repair guy can pressure / vac test it, you will know much more. 

Very low hours, you may be able to replace the piston, if the cylinder trues up.


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## [email protected] (May 1, 2007)

Here's the damage...











One thing that still bugging me though, would this cause the saw not to fire? Seems like it would start but just not have as much compression. The gasket seemed to be good shape also, no visable damage or evidence of it leaking.

I'm not sure what I'm looking for, when we talk about the crank shaft seals. I understand what your talking about, but do I have to tear down more of the saw to find/replace them? So far this seems pretty straight forward and I can probably put the cylinder kit in myself, h*ll I have already done the tear-down. I took a look at the intake hose and it looked to be pretty good. Didn't see and cracks or anything, the rubber seems to still be pliable. The clamp was on it tight also. Any recommendations are welcome (i gotta learn some how, us poor folks gotta learn to do for ourselves! )

Oh yeah, one more quick question. If I do buy the rebuild kit from bailey's, will it have the compression relief valve in it or do I have to buy that also and put it on? Wasn't obvious how that thing went on or come off.


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## sILlogger (May 1, 2007)

ouch!!! that is painful to see! as for the firing question....i suppose it could have sheared the flywheel key on the sudden stop, not sure, but anything is possible...that could have caused the saw not to fire.....the cylinder looks rough..but it might true up once a hone has been taken to it, if the coating isn't completely ate through(can't tell)...only one way to find out... personally im not thinking that it was the crank seals. but thats just me...was the saw running lean??? had the air filter been cleaned??? just a few ideas


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## sILlogger (May 1, 2007)

as for the compression release you'll have to take the old one off off your cylinder. remove the rubber grommet from the top and i think it takes something like a 1/2" socket to get it off and it treads out of the cylinder. baileys does have some that will fit the cylinder, but they are blue button husky style ones.


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## [email protected] (May 1, 2007)

The saw seemed to be running at high rpm's, guess to high. At the time I didn't realize that an air leak could cause this. The saw always seemed to 'scream' pretty good when you opened the throttle all the way up.

So you think the bailey's kit is way to go at this point? For some one who is pretty ignorant about this stuff?

How do I check this flywheel key? The motor wasn't even trying to fire. When I pull the plug out and place it on the motor and pull the string I do get spark. When I put the plug back in and attempt to start the motor I get nothing. There was fuel blowing out of the compression relief valve but the motor would never try and fire. Maybe I just had it flooded and it couldn't fire, but I don't think so (at least not when I started, I yanked on this thing for 30 minutes). Guess I could start by putting in the cylinder kit and work from there?


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## Sprig (May 1, 2007)

[email protected] said:


> The saw seemed to be running at high rpm's, guess to high. At the time I didn't realize that an air leak could cause this. The saw always seemed to 'scream' pretty good when you opened the throttle all the way up.
> 
> So you think the bailey's kit is way to go at this point? For some one who is pretty ignorant about this stuff?
> 
> How do I check this flywheel key? The motor wasn't even trying to fire. When I pull the plug out and place it on the motor and pull the string I do get spark. When I put the plug back in and attempt to start the motor I get nothing. There was fuel blowing out of the compression relief valve but the motor would never try and fire. Maybe I just had it flooded and it couldn't fire, but I don't think so (at least not when I started, I yanked on this thing for 30 minutes). Guess I could start by putting in the cylinder kit and work from there?


Obviously you are not still trying to start it, looks like you ate some rings there, probably hard to start because you had no (or very little) compression, more than likely a darned good thing it didn't fire up again too 
Now why the heck was a motor-newb like me postin' here, oh ya, may it be an idea to check the crank & bearings while you are in there? Q actually, just wondering why it failed but also wht other damage it could have done if it did a dead stop thingy. Lots of very knowlegable folks here (and welcome), with a bit of patience and some sort of monkey wrenching exp. you should be able to get it back to its former self, but as the guys have said so many times, gots to find why it did that in the first place with so little time on it. Nother Q, would a leaned out mix/adjust do this sort of thing too? Just wondering again.

 And have fun on the learning curve!

Serge


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## [email protected] (May 1, 2007)

Were on the same page, I'm just wondering if getting a new cylinder kit on it will be the quickest way to find out what the real problem is. When I get it started maybe I can have someone who knows more than me see if there is any issues with how its running. With some great advice from the guys on this forum I can at-least see what the problem is and hopefully get the ol' girl purring again. Tomorrow, I'll investigate some more.


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## ShoerFast (May 1, 2007)

[email protected] said:


> The saw seemed to be running at high rpm's, guess to high. At the time I didn't realize that an air leak could cause this. The saw always seemed to 'scream' pretty good when you opened the throttle all the way up.
> 
> So you think the bailey's kit is way to go at this point? For some one who is pretty ignorant about this stuff?
> 
> How do I check this flywheel key? The motor wasn't even trying to fire. When I pull the plug out and place it on the motor and pull the string I do get spark. When I put the plug back in and attempt to start the motor I get nothing. There was fuel blowing out of the compression relief valve but the motor would never try and fire. Maybe I just had it flooded and it couldn't fire, but I don't think so (at least not when I started, I yanked on this thing for 30 minutes). Guess I could start by putting in the cylinder kit and work from there?



Your flywheel key may be fine, but you are telling me a couple of things here, and the pictures,,, good pic!

That Saw seized from lean failure, but your telling me something here, that it was a screamer,,,, if you think it was running to fast, I think your right. Fast is too lean (to a point) 

If it had a good idle, and started good cold, your still going to want to check everything, but I'm not as afraid of it,,,,, I think it may have been lean since new, if you have never checked it?

I just bought a new MS-361 , asked my dealer if I could hear it on his tach to get an idea,,,, and it was screaming at 17K, we cut the tabs off , it may not have made it 20 hours that lean?

If your saw was not set up right, or never adjusted right, 20 hours may be about right.

Do a couple searches if you would like, check on using acid to clean cylinders, hones in cylinders and on carb tuning and on how to cut the limiter caps-tabs off. 

From what you said so far, if you put a cylinder and piston kit in it,,,, or a piston and rings if the cylinder trues up, it will start for you,,,,,, but your going to want to turn the "H" screw out to a full 1 1/4 - 1 1/2 turn to start with. maybe have someone walk you through setting the carb?

There would not be many here that would bet that not fatting the carb up, just starting it with a new cylinder and piston, that it would run well past 15K? It should be around 13K free speed.


Have fun!


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## [email protected] (May 2, 2007)

ShoerFast said:


> There would not be many here that would bet that not fatting the carb up, just starting it with a new cylinder and piston, that it would run well past 15K? It should be around 13K free speed.



Huh? I'm not up to speed on my chainsaw jargon.  So If I got you right, I need to do the cylinder kit, make the adjustment on that mixture screw, get it started, have someone tune the carb correctly.

When I bought this saw this was the first stihl I had ever owned. Thought what it was doing must be normal. Guys at the shop where I bought it said it was tuned and ready to go. Guess by tuned they meant they took it out of the box. From what I understand from bailey's my saw had the incorrect sprocket on it also. Bailey's sent me a replacement for free, nice folks.


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## tek9tim (May 2, 2007)

Well, at 20 hours, you shouldn't have a problem with an air leak, but perhaps you do, maybe you should have your case checked. Probably easiest to have a dealer do this for you. Odds are that you don't, but you could at least eliminate variables. You didn't happen to be at the end of your tank of gas, did you? I melted down the piston on an 046 trying to get 1 more little cut in. 

Wrong sprocket? That's a matter of opinion most of the time. Unless it's the wrong pitch for the chain they sold you.

Edit to add: somebody mentioned cleaning the air filter... a dirty filter will richen up the mixture, thus reducing heat. Also, I know some loggers that'll go way more than 20 hours of hard cutting without cleaning their air filter. (not that I'm promoting such a practice, but it won't kill a saw that quickly)


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## sILlogger (May 2, 2007)

here is what i think happened, based on what u have said and past experience. my guess is that the carb on the saw was not adjusted properly and has been running too lean since the saw was new. the saw was turning too high of rpms, starving for oil=scoring, piston got hot and swelled and locked up inside the cylinder=thus more scoring. that cylinder might be able to be cleaned up with a good honing, possibly, i'm running an 066 right now that had a pretty scored up cylinder that i cleaned up by honing. but if u want to remove all doubt buy a piston and cylinder kit. flush out the crankcase a few good times with premixed gas to get any metal particles out and install the piston and cylinder. some people are different but i use white lithium grease (assembly lube) on the cylinder walls and piston when putting them back together. once back together thread the H screw on the carb all the way in (clockwise) and back it out around 1 1/4 turns counterclockwise. just as well start with a new spark plug. and then start the saw. it should fire up for you. i'm guessing u don't have a tach and prolly dont' wanna tune by ear so i would take it to someone with a tach and have then tune it to around 12500-13000 rpms with a bar and chain. 

chainsaw jargon
"screaming" not always good, in this case too my rum rums and saw was lean
"fatten' up the carb" turning up the fuel, or "richening" the saw to allow more fuel and lowering rpms. 
"high speed come apart" what this saw did, and what i do on occation

Hope this helps!!


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## sILlogger (May 2, 2007)

o yea, im gonna pull back on the sheared flywheel key idea, after looking at the cylinder the key prolly didn't shear. and when i was asking whether the air filter had been cleaned i didn't know if the saw had ingested something. personally i tap out my air filter about ever 3 tanks of fuel.


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## [email protected] (May 2, 2007)

I don't air cleaner was an issue. The filter was clean. I clean the pre-filter after every job or when i have to change/adjust the chain.

The sprocket issue probably is a matter of opinion. With this saw and the old sprocket it was VERY easy to get the chain so hot it would loose its temper. I' m not talking about a chain is dull as a butter knife. I'm talking about fresh chain. Bailey's precut loops wouldn't even fit on my saw. I talked with them for a while about the issue and they had me go out and check the sprocket. I don't remember how big it was but he said it was to big for a saw with this horsepower. They sent me a new sprocket and I didn't have trouble with the chains burning up anymore. They guy at bailey's said that sprocket was for a saw that is underpowered and needs to increase chain speed to overcome its lack of torque.

Probably didn't help that the saw was apparently running lean also.

I'm gonna talk it over with the little lady tonight and will probably go ahead and order the bailey's kit. Some one with more experience than myself could probably hone the current cylinder. The drags really aren't that deep. Alot of the worst looking places are actually where the metal from the piston soldered itself to the wall of the cylinder. I used to work at a factory that made pistons like these. If you let the die get to hot the same things happens to the die.

Is there any certain technique to remove these clips to free the piston? Haven't tried to remove the piston yet.

SILogger, can you recommend someone in our neck of the woods to tune this saw when I get it back together? And maybe check it for leaks?


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## sILlogger (May 2, 2007)

Fb McAffoos in Benton IL is who i have do any service work that i need done. always had good luck with them. not sure how far that would be for ya, but they have always took good care of me


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## oregonlumber (May 5, 2007)

i am new to this site, but have had the same problem with my 066 metal tab.
what fried my piston was that the clutch drum sproket and needle cage were to large and the carb was set a little on the lean side running about 14000 to 14500rpm. new piston, clutch drum,ect.. and i went ahead and changed out the bearings as well as crank seals and gasket. i couldnt see rebuilding top end, only to find that something in the bottom end going out and blowing it up again. now i have a old saw that runs like new.


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## West Texas (May 7, 2007)

You can buy a long handle screw driver like torque's wrench at Sears, usually a 27 will do it. If its really tight, you can grip the handle of the wrench with a cresent wrench or a pair of pliers to break it loose, then screw it on out easily.


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## [email protected] (May 10, 2007)

Hey guys, is there a trick to getting those retaining rings (or whatever they are called) out of the piston assembly so I can remove the piston? Is there a special tool? Looked little tricky to remove them. Just thought I would ask before did something stupid trying to get them out.
:stupid:


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## [email protected] (May 10, 2007)

Got my rebuild kit today, any last hint tips or suggestions before I attempt to install this thing? The inside of the cylinder is already oiled down, is that enough lube to protect the motor at initial startup? Should the fuel have extra oil in it the first few tanks? Any help that would prevent me from screwing up here would be appreciated.


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## [email protected] (May 10, 2007)

*Running at last, oh my god, running at last*

First off...*I would like to thank everyone for all their tip/hints/suggestions.* I truly appreciated it. I went from being told I needed to buy a new saw (about $900) to fixing mine for $120 dollars. A true testament to your expertise, and patience. This kind of generosity is what the internet should be about, well, maybe a little **** too.  If you ever find your way to Kentucky, the beers on me.

I couldn't wait for any more suggestions before I started. So i went out and give her a shot. Took me about 2 hours to put it all back together. The hardest part was getting that piston in the cylinder. I don't have a ring compressor so i had to make due. I did most of it twice because I was such a hurry I forgot to put the cylinder gasket back on first. So i had to take the cylinder and piston back off to put it on. Should be getting pretty good at it now. Anyway, after getting everything bolted back on I had to try and start her. She fired up on the second pull. Never expected that. This saw hasn't been started in about a year and a half. Never heard such a beautiful sound. I took special care that it didn't get rev'ed up to high. Just let her idle for a minute. Before using her I'm gonna take her to be tuned. Hopefully I can find someone locally who knows what they are doing.


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## oregonlumber (May 10, 2007)

good i always like to here that an old saw has got new life. the only other thing that i would recommend is that you have the saw set to a low rpm and run 3 or more tanks of fuel through it and go through some chips!!

ya without the guy here on the arborist site i dont know if i would of gotten my old saw running again


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