Stihl 026 Clutch Self-destructed! Pics to follow...

[rallen]

Even though I have a better looking (and well-maintained over its history) 026 that I acquired, I find I enjoy using the one that I was given as a burnt out hulk, and rebuilt with a new piston, salvaged cylinder, and oil seals (see my re-build thread if curious..lots of pics). At first I started to use the re-built saw just to make sure my re-build held up, but I enjoyed the sound of it so much that I now tend to reach for it first, even though on the outside, she is definitely not the prettiest girl on the block.

HOWEVER....

Last time I used it, I noticed that it seemed to to scream at full throttle. My suspicion was that she was running a little too lean, and I told myself I should get my little screwdriver and adjust the carb. Of course, being a procrastinator and only having a little wood to cut that day, I thought I would take care of it when I finished my task at hand.

Very likely, that was the wrong choice.

After fifteen less than and hour of use, it stopped mid-cut, as if someone had thrown the chain brake. And that is sort of what happened, except it wasn't someone, it was the saw: the clutch drum was locked solid. At first I was worried that perhaps my re-build failed and the piston has froze in the cylinder somehow, but nope, when I pulled it apart, all was explained. The clutch had self-destructed, not only breaking one of the three shoes, and bending some of the springs, but breaking the actual "spider" apart from the shaft. In so doing, the fractured and flying parts seeking to exit the clutch drum chose to chew up the oil pump and hose as well as make the the clutch drum oval in their valiant attempt to escape their confines. In other words....DISASTER.

So $75 or so later, I have ordered a new oil pump assembly from a salvaged saw, along with a used clutch and clutch drum. Since I had to replace everything anyways, I decided to upgrade the oil pump to the adjustable style. I probably spent as much on these replacement parts as I did on the re-build parts, or perhaps more, but, I like the saw, and know its worth the value, and plus, I feel responsible for its failure whether I should or not.

So what would have caused this calamity? I don't think the saw was over-revving THAT much. But why did the spider crack? Was I just "lucky"? A spring let go and a shoe jammed, and voila??? Or did the spider just decide to end it all, and in so doing take out its nearby friends??? I am curious more than anything else, but I don't know the history of this saw other than it was burnt up when I got it, and who knows what abuse she endured before finding a loving home with me.

On the good side: I had debated when I re-built her replacing the oil pump with the adjustable type, but couldn't justify the cost at that time. Surprisingly, the combined price for the adjustable oil pump now comes out to about the same cost as replacing the pump with the the non-adjustable style, since regardless, I have to replace clutch drum and oil pump. So my lowly 026 will now evolve into an 026 "Semi-Pro".

Any thoughts on the cause of the clutch failure? Have others experienced this 'special event' while cutting wood? It's not like it was straining; if anything, I would blame it on not being under much load so it could free rev to its maximum...

Live and learn...LOL. I need to post a pic of all the pieces; it really is impressive what damage it did in flying apart. I threw a chain earlier that same day...think it was a sign to just STOP.

Robert

 

[nmurph]

...think it was a sign to just STOP.

Robert

Don't forget to find out why the saw is screaming or you may find another sign...on the piston.

 

[7sleeper]

Don't forget to find out why the saw is screaming or you may find another sign...on the piston.

You might even say "listen the saw is already screaming at you!"

And by the way where were the pics?!

7

 

[rallen]

QUOTE=7sleeper;4528428]You might even say "listen the saw is already screaming at you!"

And by the way where were the pics?!

7[/QUOTE

I like that thought.

My challenge is that I know a little but I don't have alot of experience, being an occasional user. I never understood what that term meant until reflecting on my calamity afterwards. I think you hit the nail on the head: the saw was screaming at me to pay attention and not ignore what I was hearing that didn't seem right.

I share my exxperience for other occasional users who may be victim to the same oversight. Most likeky the failure was caused by a combination of age, speed, and circumstance, amd if I acted sooner to address the speed perhaps I coukd have avoided this lesson.

But hey, I finally am getting that adjustable oiler!
I promise to post pics but jave to take 'em first tonight. Thanks to all for the cautionary advice.

Robert

 

[rallen]

Even though I have a better looking (and well-maintained over its history) 026 that I acquired, I find I enjoy using the one that I was given as a burnt out hulk, and rebuilt with a new piston, salvaged cylinder, and oil seals (see my re-build thread if curious..lots of pics). At first I started to use the re-built saw just to make sure my re-build held up, but I enjoyed the sound of it so much that I now tend to reach for it first, even though on the outside, she is definitely not the prettiest girl on the block.

HOWEVER....

Last time I used it, I noticed that it seemed to to scream at full throttle. My suspicion was that she was running a little too lean, and I told myself I should get my little screwdriver and adjust the carb. Of course, being a procrastinator and only having a little wood to cut that day, I thought I would take care of it when I finished my task at hand.

Very likely, that was the wrong choice.

After fifteen less than and hour of use, it stopped mid-cut, as if someone had thrown the chain brake. And that is sort of what happened, except it wasn't someone, it was the saw: the clutch drum was locked solid. At first I was worried that perhaps my re-build failed and the piston has froze in the cylinder somehow, but nope, when I pulled it apart, all was explained. The clutch had self-destructed, not only breaking one of the three shoes, and bending some of the springs, but breaking the actual "spider" apart from the shaft. In so doing, the fractured and flying parts seeking to exit the clutch drum chose to chew up the oil pump and hose as well as make the the clutch drum oval in their valiant attempt to escape their confines. In other words....DISASTER.

So $75 or so later, I have ordered a new oil pump assembly from a salvaged saw, along with a used clutch and clutch drum. Since I had to replace everything anyways, I decided to upgrade the oil pump to the adjustable style. I probably spent as much on these replacement parts as I did on the re-build parts, or perhaps more, but, I like the saw, and know its worth the value, and plus, I feel responsible for its failure whether I should or not.

So what would have caused this calamity? I don't think the saw was over-revving THAT much. But why did the spider crack? Was I just "lucky"? A spring let go and a shoe jammed, and voila??? Or did the spider just decide to end it all, and in so doing take out its nearby friends??? I am curious more than anything else, but I don't know the history of this saw other than it was burnt up when I got it, and who knows what abuse she endured before finding a loving home with me.

On the good side: I had debated when I re-built her replacing the oil pump with the adjustable type, but couldn't justify the cost at that time. Surprisingly, the combined price for the adjustable oil pump now comes out to about the same cost as replacing the pump with the the non-adjustable style, since regardless, I have to replace clutch drum and oil pump. So my lowly 026 will now evolve into an 026 "Semi-Pro".

Any thoughts on the cause of the clutch failure? Have others experienced this 'special event' while cutting wood? It's not like it was straining; if anything, I would blame it on not being under much load so it could free rev to its maximum...

Live and learn...LOL. I need to post a pic of all the pieces; it really is impressive what damage it did in flying apart. I threw a chain earlier that same day...think it was a sign to just STOP.

Robert

The plot thickens, or rather, thins??? I received the replacement parts, and am happy to say my 026 "semi-pro" is now alive and well and ready to chip wood. In preparation for this maiden event, I decided I should touch up the chain, and THIS time, I finally thought I would try to use that little device in my sharpening kit used to adjust the raker height. And guess what? Many of them were quite high. So...my poor 026, at full throttle, was just making grooves in the wood, no load to speak of, which meant the poor little tired clutch was racing along and finally gave up on life.

It has been a somewhat expensive lesson, but it is always good to learn things. And, as promised, here are the pics of the remains:

View attachment 316240View attachment 316241

 

[SkippyKtm]

View attachment 316243

Looks to me like the clutch carrier flew apart, there may have been tiny cracks from over tightening and it finally just flew apart. I had an 044 with the clutch so tight that no matter what I used(impact, breaker bar, etc) it would not loosen. I finally had to cut part way through the carrier(spider) in two places and crack it off with a chisel. I've also seen catastrophes occur when the clutch springs have gotten so worn that one of them finally broke and jammed in the oil pump, but that doesn't look to be the case here.