tree removal - chaisaw problem, wrog fuel mix

[MotorSeven]

Check your fuel and impulse line. They get gummy and collapse when under full throttle. While you're at it check the fuel filter on the end of the line in the tank. I would also get a rebuild kit for the carb and change everything out.

As for fuel, yes your saw will run better on regular gas. That being said, I run race fuel 110 octane in all my saws because it does not contain ethanol. I have to adjust the idle up on all saws running 110.

 

[jim44]

My stihl polesaw was giving me the same symptoms. I finally put about 1/4 cup of seafoam in a half tank of fuel, and after running a few minutes, it's all better. Still have no idea exactly what the problem was...... . No ethanol gasoline is a must for all small engines.

 

[Oliver1655]

Just for grins, how does your fuel tank vent? I have older Stihl saws that have a 2" piece of fuel line with a set screw which is PUSHED into it for a vent. ** Note PUSHED not screwed. ** I had a time when the symptoms were similar to yours & it was because it was not venting properly. (Turns out I had dropped the saw off at a saw shop to have a couple of loops of chain made to go with the 25" bar I had ordered in. They noticed moisture when they had turned the saw on it's side, investigated & found a crack in the fuel line & as a courtesy to me replaced the fuel line & vent line. Unfortunately the helper doing the work did not know about pushing the setscrew in & instead screwed it in which caused the threads to cut into the fuel line & sealed the venting action. On another occasion, cutting out stumps, the same problem, I pulled the set screw out cleaned the threads & pushed it back in & it took care of the problem.

 

[Jasonc87]

The argument of a numerically low oil ratio, or higher concentration of oil in the fuel mixture is it leans the air/fuel mixture. You have the same amount of air coming in with half the fuel in the above instance makes a lean air/fuel mix. Yes it has twice the lubricant but, lean mixes run hot. The more oil in the mix the less fuel to burn, the leaner and hotter the air fuel ratio gets.

Still doesn't sound like that's what you have going on though especially after a full visual inspection. Fuel filter, fuel vent, lines, and diaphragm is all that makes the fuel delivery outside the internals of the carb...

 

[PapaPerk]

Putting 1:25 mix in a saw that takes 1:50 should not damage saw. Ur just putting more oil through it.

If the saw won't come up from idle try leaning out the high speed mixture screw some. Once the saw burns through the thick mix it will then need readjusted to the richer mixture setting.

If you are a novice at carb adjust u should take to dealer.

 

[tractchores]

Just for grins, how does your fuel tank vent? I have older Stihl saws that have a 2" piece of fuel line with a set screw which is PUSHED into it for a vent. ** Note PUSHED not screwed. ** I had a time when the symptoms were similar to yours & it was because it was not venting properly. (Turns out I had dropped the saw off at a saw shop to have a couple of loops of chain made to go with the 25" bar I had ordered in. They noticed moisture when they had turned the saw on it's side, investigated & found a crack in the fuel line & as a courtesy to me replaced the fuel line & vent line. Unfortunately the helper doing the work did not know about pushing the setscrew in & instead screwed it in which caused the threads to cut into the fuel line & sealed the venting action. On another occasion, cutting out stumps, the same problem, I pulled the set screw out cleaned the threads & pushed it back in & it took care of the problem.

Thanks. This is one thing I have not checked. I believe the vent is through a long pin that sticks into the fuel tank and holds the fuel line / filter. I've had it out before, but could not remember how to remove it this time. I did not check that, but that might be a good place to look - especially if extra oil clogged it or caused it to gum up. Clearly the saw is not getting the right ratio of oil / air when revving high since everything else checks out. The air filter etc look fine, so my guess is that I've got a partially clogged high-speed jet in the carb, or some kind of fuel delivery problem. It doesn't sputter and smoke, so I'm leaning towards too little fuel VS too much at this point.

My plan is to take it to the dealer for a quick check VS playing with the mix myself. My fear with messing with it is that if I lean it out too much I could damage the engine since it's 2 stroke. Hopefully I'll get it there Friday and find out what the issue is!

 

[SoGeorgia]

I gotta ask because one of my chainsaws exhibited the same symptoms one day.

Is the anti kickback handle in the right position? ie. pulled back towards you? If its forward it won't rev. I didn't even realize mine got tripped.

 

[LD1]

Yes, the chainbrake handle needs pulled back toward you. Forward sets the brake and wont allow the chain to spin, therefore it wont rev either.

 

[tractchores]

I gotta ask because one of my chainsaws exhibited the same symptoms one day.

Is the anti kickback handle in the right position? ie. pulled back towards you? If its forward it won't rev. I didn't even realize mine got tripped.

Yes, the chainbrake handle needs pulled back toward you. Forward sets the brake and wont allow the chain to spin, therefore it wont rev either.

Thanks. The chain brake is not on, I can rev it up for a moment and then it stalls after a few seconds. I can even cut a bit with it, but it loses power and bogs, then will rev up again. Anywhere up to full throttle it runs totally fine and will cut, but slowly.

 

[arrow]

Unfortunately tc one cannot guarantee that visual inspection will suffice for either a diaphragm or fuel lines. I could show you many a fuel line that looks perfectly fine but ends up porous as all get out. Diaphragms are the same way. If your saw idles fine but giving it gas it stalls, that can most certainly be a porosity issue. The other clue is that it ran fine for a moment but then it acted up again. I've seen fuel line cracks do this exact thing. It is just possible that you have an air leak that just happened to rear its head finally when you put in the wrong fuel mix. I'd take Motor 7's advice and change out the fuel lines.