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Hi all,

What a fantastic forum.

I know this isn't a lawnmower problem so please, bare with me. A few years ago my late dad purchased a Stiihl 021 chainsaw. It ran great when he operated it, which wasn't much. But, he died 4 years ago and it had been sitting since then. I had a load of logs delivered to my property to buck up and split for next winter's heat supply. Approx. half way through the log pile the unit began acting up. Acting up in the sense that it began sputtering. Hold the throttle wide open and absolutely no power from it. I cleaned the carb knowing it had been sitting for awhile. Now, that thing was in bad shape. I took all the gaskets and screens out if, soaked it in gumout for 24 hours and rebuilt the carb. It ran like a charm for nearly an entire day. The 2nd day of operation, performed as described above after about an hours worth of running time. No matter what I do to it, it does not have any power to turn the chain. I checked to be sure I didn't accidently push the anti-kickback mechanism forward (which I have done a few time), I didn't touch it, the chain rotated freely when pulllin on it by hand. It's got to be something simple that I'm missing but darned if I can figure it out. Any help will be greatly appreciated. Thanks in advance for any/all advise. Roger

I had a similar problem with a Craftsman (Poulan) chainsaw. The engine seemed to lack the power to turn the chain but I could still turn it by hand. It turned out to be the centrifugal clutch assembly.

So the engine runs okay now but the chain doesn't turn? My 026 Stihl did this once and it turned out to be the anti-kickback mechanism. Took it to the dealer and he pushed it back ... I felt like a complete idiot! :ashamed: Anyway you said you checked that so that's not the problem. As Hand2ThePlow suggested, the centrifugal clutch may not be contacting the chain drive sprocket thus no friction to drive the chain. Remove the bar and chain to check if the sprocket spins when the engine is running at high speed. The problem can probably be fixed by replacing the sprocket. They eventually wear out just like chains.

I have to pipe in and say we own a Stihl and it has hours and hours of use on it. We have never had an issue and feel like it was worth the investment (since it wasn't cheap!). I don't know what's wrong with yours but I hope it is a simple fix.

My Stihl 023 has a red plastic baffle at the air cleaner inlet. It is supposed to be up in the summer and flipped over and pushed down into two grooves pulling the inlet air over the engine during cold weather ( less than +14 deg F). If it is down and the engine is run for along period it will be down on power, but run ok when still cold. Have you replaced the spark plug? I would get an owners manual from Stihl.

Try this link for the manual


http://dl.owneriq.net/d/d23aca42-ef68-46af-adac-3c63327cf0ba.pdf

Okay, let me state that I'm not badmouthing the Stihl chainsaw. I had an 031 for years until a tree fell on it and destroyed it. Aside from the occassional carb cleaning, it ran great. The 021 however, is giving me a headache not knowing where to look for the source of the lack of power.

I'll try to do a better job describing what's happening; Hold the throttle wide open, the motor bogs down, acts like the carbs dirty, highspeed jet is clogged. Let me add here that I also drained the gas tank thinking that I had dirt in the tank. That didn't work either, but at least I removed it from the picture as a possibilty. Still, engine bogs while holding throttle open.

I wouldn't want to run the saw too long without it but is there a way to disable the chain lock, essentially removing it as a possibility? If it is the problem, I'll have the repair shop fix it so I can use the saw with it fully operational. Again, thanks for taking the time to off up your suggestions. Roger

Roger2561 said:

Okay, let me state that I'm not badmouthing the Stihl chainsaw. I had an 031 for years until a tree fell on it and destroyed it. Aside from the occassional carb cleaning, it ran great. The 021 however, is giving me a headache not knowing where to look for the source of the lack of power.

I'll try to do a better job describing what's happening; Hold the throttle wide open, the motor bogs down, acts like the carbs dirty, highspeed jet is clogged. Let me add here that I also drained the gas tank thinking that I had dirt in the tank. That didn't work either, but at least I removed it from the picture as a possibilty. Still, engine bogs while holding throttle open.

I wouldn't want to run the saw too long without it but is there a way to disable the chain lock, essentially removing it as a possibility? If it is the problem, I'll have the repair shop fix it so I can use the saw with it fully operational. Again, thanks for taking the time to off up your suggestions. Roger

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Loosen the bolts holding the muffler enough to allow the exhaust to leave the engine. If the muffler is carbon clogged a two cycle engine will run as you have described.

gator6x4 said:

Loosen the bolts holding the muffler enough to allow the exhaust to leave the engine. If the muffler is carbon clogged a two cycle engine will run as you have described.

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HAD THIS HAPPEN ONCE---------ON A STIHL O41 Farm boss---- cut 10 cords a yr with this old beauty until dealer said was just worn out-23 yrs old

gator6x4 said:

Loosen the bolts holding the muffler enough to allow the exhaust to leave the engine. If the muffler is carbon clogged a two cycle engine will run as you have described.

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Yes, the muffler or the spark arrestor can cause back pressure that will cause those symptoms. Is there a fuel filter inside the gas tank ?

Side note: I had a Kawasaki 500 3 cyl. 2 stroke that was bogging down after run for a while -- I FINALLY found that it was the exhaust baffles -- Cleaned them out and it ran fine.

BKBrown said:

Yes, the muffler or the spark arrestor can cause back pressure that will cause those symptoms. Is there a fuel filter inside the gas tank ?

Side note: I had a Kawasaki 500 3 cyl. 2 stroke that was bogging down after run for a while -- I FINALLY found that it was the exhaust baffles -- Cleaned them out and it ran fine.

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Will the motor run strong for a short time (10 to 15 minutes) and then act as it has as the engine warms up if it is the spark arrestor? What's the purpose of the spark arrestor. Is it a machanical item versus an electrical item? Where is it located?

And, yes, there is a filter in the gas tank. But, I still drained the gas from the gas tank and cleaned the tank to be sure that I covered all bases regarding fuel delivery. I have not installed a new filter, yet. Roger

Roger2561 said:

Will the motor run strong for a short time (10 to 15 minutes) and then act as it has as the engine warms up if it is the spark arrestor? What's the purpose of the spark arrestor. Is it a machanical item versus an electrical item? Where is it located?

And, yes, there is a filter in the gas tank. But, I still drained the gas from the gas tank and cleaned the tank to be sure that I covered all bases regarding fuel delivery. I have not installed a new filter, yet. Roger

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A spark arrestor most of the time on a chain saw is either a flat or cone piece of mesh wire. When metal is subjected to heat it expands. Hot exhaust exposes all parts of the exhaust system to heat. The purpose of a spark arrestor is to prevent carbon sparks from the exhaust on an internal combustion engine from igniting dry leaves or other combustibles.

Roger2561 said:

Will the motor run strong for a short time (10 to 15 minutes) and then act as it has as the engine warms up if it is the spark arrestor? What's the purpose of the spark arrestor. Is it a machanical item versus an electrical item? Where is it located?

And, yes, there is a filter in the gas tank. But, I still drained the gas from the gas tank and cleaned the tank to be sure that I covered all bases regarding fuel delivery. I have not installed a new filter, yet. Roger

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Last post explained what the spark arrestor is - it is usually on the outside of the muffler port (you may need to remove housing to get at muffler and arrestor) Yes, it will sometimes run for a while before the back pressure slows everything down and even stops the engine. If I understand correctly the back pressure just does not allow the exhaust gases out (no place for them to go) I usually use a wire brush on a drill to clean off carbon on the arrestor screen. Take it out - clean it - put it back -- if it is the muffler - sometimes they come apart allowing inside to be cleaned - sometimes a new muffler is the best bet. Good Luck !

I want to thank everyone for taking time out of your busy schedules for your input. The spark arrestor is something I have never heard of before so it's something that I'll look into when I get few minutes. I'll post the results after I takle it. Thanks again. Roger

PS; I repeat my previous remark - what a great forum. So many people who have knowledge and not afraid to share it with others.

Okay - I removed the spark arrestor from the exhaust and cleaned it. It wasn't that dirty but I decided to clean it anyway. I reassembled everything after the cleaning, started the saw and it ran like a charm. It had full power for the hour I operated it. Thanks for the tip. I have learned something new.

Roger

Glad that seemed to solve the problem :biggrin: -- could you tell if the muffler would come apart -- may be carbon buildup inside that also -- most problems of this nature seem to come from poor grade 2 stroke oil or using too much oil in the gas mixture.

Roger2561 said:

Okay - I removed the spark arrestor from the exhaust and cleaned it. It wasn't that dirty but I decided to clean it anyway. I reassembled everything after the cleaning, started the saw and it ran like a charm. It had full power for the hour I operated it. Thanks for the tip. I have learned something new.

Roger

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BKBrown said:

Glad that seemed to solve the problem :biggrin: -- could you tell if the muffler would come apart -- may be carbon buildup inside that also -- most problems of this nature seem to come from poor grade 2 stroke oil or using too much oil in the gas mixture.

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I think you hit the nail on the head. I spoke with my sister earlier today telling her of the problem I had experienced. My nephew helped me cut the log pile while I was at work. For some reason she mentioned that he had to mix more gas/oil and used the ratio set to his chainsaw, which is a heavier oil mixture. While I had the spark arrestor off and the muffler in my hand, I pushed some compressed air through it. Perhaps that made a difference. Roger

Roger2561 said:

I think you hit the nail on the head. I spoke with my sister earlier today telling her of the problem I had experienced. My nephew helped me cut the log pile while I was at work. For some reason she mentioned that he had to mix more gas/oil and used the ratio set to his chainsaw, which is a heavier oil mixture. While I had the spark arrestor off and the muffler in my hand, I pushed some compressed air through it. Perhaps that made a difference. Roger

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Usually the Sthil brand of 2 stroke oil requires less oil in the mix and Stihl recommends less oil in the gas than some other saws. Compressed air blown through the muffler probably cleaned it out some (even if you didn't see any debris) GLAD you can use the saw without an expensive visit to the repair shop !! :biggrin: :thumbsup:

Hi Roger, I moved your thread to the new Stihl Forum. :smile: