Echo CS 680 stop cutting/running under pressure

[epo]

No idea what you are trying to clarify. With your saw running at idle just below chain motion, put the chain brake on and give it some throttle. What rpm does it stall at?

A more fitting experiment here would be to use full throttle (you use WOT when cutting, don't you?) and engage the brake or pinch the B&C in the wood.

My point is that the clutch starts to slip at higher speeds than what we call the clutch engagement speed.
In the case of the saw whose graph I posted above, this starts happening near 5800 rpm.
Below this speed, the torque of the saw's engine is able to overcome the frictional force occurring between the clutch shoes and the inner surface of the drum.
Then they begin to rub each other, accompanied by a sharp increase in their temperature.

The fact that the clutch works this way is to protect the engine from overloading, and also prevents it from stalling, which would be a nuisance during use.
Of course, upon hearing this recognizable sound, the operator should let go of the throttle lever to prevent the clutch from overheating.

 

[Old2stroke]

A more fitting experiment here would be to use full throttle (you use WOT when cutting, don't you?) and engage the brake or pinch the B&C in the wood.

My point is that the clutch starts to slip at higher speeds than what we call the clutch engagement speed.
In the case of the saw whose graph I posted above, this starts happening near 5800 rpm.
Below this speed, the torque of the saw's engine is able to overcome the frictional force occurring between the clutch shoes and the inner surface of the drum.
Then they begin to rub each other, accompanied by a sharp increase in their temperature.

The fact that the clutch works this way is to protect the engine from overloading, and also prevents it from stalling, which would be a nuisance during use.
Of course, upon hearing this recognizable sound, the operator should let go of the throttle lever to prevent the clutch from overheating.

I don't think it would make much difference, regardless of what rpm the engine is at, when the chain stalls with the power on, the engine should reach the same equilibrium point where the engine torque is balanced by the friction load from the clutch and this point would be different for every saw. An important take-away here is that the "starts to slip" point at the high rpm (chain still moving) could be considerably higher than the "equilibrium" point where the chain is stalled and it might be possible for an operator to be running the saw in this rpm zone, resulting in serious clutch heating. Again, not a clutch fault, operator error.

 

[Qasim Khan]

Ok, so I got new clutch and clutch drum replaced them and same issue. I made a video this time of the issue. Please see.

 

[Bob Hedgecutter]

So- what happened to the photos of the chain cutters and their relationship to the depth gauges?

Where is the brake flag?

 

[epo]

Ok, so I got new clutch and clutch drum replaced them and same issue. I made a video this time of the issue. Please see.

You mentioned adjusting the H needle on the “old” carburetor. Do you know how you have it adjusted on this new one?
The basic settings are 1 1/8.

 

[Qasim Khan]

You mentioned adjusting the H needle on the “old” carburetor. Do you know how you have it adjusted on this new one?
The basic settings are 1 1/8.

Yes, I did on new one.

 

[Qasim Khan]

Am I clearly showing issue in my video?

 

[epo]

Yes, I did on new one.

So at the moment you have it open 1 1/8 turn from its seat? Or did you adjust it by some other method?

 

[Qasim Khan]

I adjusted to optimum performance. It does not run lean or rich. As you can see in my video.

 

[LuDookie]

Looks to me like you are just dogging it in.

 

[Bob Hedgecutter]

Okay, I'm out- writing it off as operator error and incomplete machine.

 

[epo]

Okay, I'm out- writing it off as operator error and incomplete machine.

The OP wrote that he replaced the guide bar and chain with new ones. And that didn't help. I don't think he tinkered with the depth gauges before trying them out.

He removed the brake band (and maybe more) because there was a problem or operator error and the clutch drum showed signs of overheating from the band.

 

[Qasim Khan]

@LuDookie I am was just using it as I used to do. It chain stop running and I and removing it from wood and try again.

 

[Old2stroke]

The problem with the video is we can't tell if the chain is stalling because you are applying too much pressure on the bar or because the saw is down in power due to fuel starvation. Assuming you are using your normal amount of pressure that use to work, then the problem should be fuel. You say the saw is running just right. It isn't. It should be running rich and making what's called a 4-stroke sound when you rev it up without cutting and clean out to crisp sound ONLY when it is cutting. Back the H screw out (CCW) 1/2 turn and see how it cuts. If that doesn't make any difference, it could be a restriction in the fuel supply like a fuel filter, pinched or leaking fuel line.
When the chain stalls, you CANNOT keep the power on because the clutch is slipping and that's why the clutch is overheating. See my post on "how to overheat a clutch"

 

[chilipeppermaniac]

You say the saw is running just right. It isn't. It should be running rich and making what's called a 4-stroke sound when you rev it up without cutting and clean out to crisp sound ONLY when it is cutting.

I saw the video and thought the very same thing. First and foremost, I see operator error.
2nd, I see possible carb adjustment issues, both technique and results.
3rd, and I can't get a long enough or close up enough view of just how sharp is the chain. ( Speaking of which, WHAT chain are you using? SIZE, Safety chain or Skip tooth or what? MY one question here is , are we sure it is the right pitch, gauge etc for the bar? Also how sharp is the chain (Really) Watch the 2nd video and see the big chips his saw is producing. If you are getting more fine dust, then you won't get a happy saw. Sharp Sharp chains make a saw work less hard.



He talks about 4 stroking like Old2stroke mentions. In addition to the tuning demo, watch how he " let's the saw EAT the wood, he doesn't force the bar/chain into the wood like you do and bring about the bogging of your saw.

 

[Qasim Khan]

I am curious about operator error, what is that? Am I not using the saw correctly? If yes, what am I doing wrong?

 

[epo]

I am curious about operator error, what is that? Am I not using the saw correctly? If yes, what am I doing wrong?

Let's assume that your chainsaw is in a state before it started giving you trouble.
The operator's error would be, first of all, to push the saw too hard, which could cause the engine speed to drop below the value at which clutch slippage begins to occur.

Normally, you should pay attention to this and reduce the pressure when you hear a clear drop in engine speed. The saw should not have problems cutting with feed force caused only by its weight.
The cause of the drop in RPM could also be the pinching of the guide bar and chain by the piece being cut.

The following can also be considered operator errors: using an improperly sharpened chain, tensioning the chain too much or too lightly, leaving the brake engaged when the saw is in fast idle mode, etc.

In your case, the problem now is that the engine does not have enough power, or more specifically, torque, to overcome the resistance that occurs when you try to cut.

The simplest case is that you are using too much pressure on the saw to force it to cut, which is a case of operator error. Can you cut that log from the video with almost no pressure on the saw? The video also shows logs with a small cross section. When cutting them, do you also have a similar problem?

Another possible cause is a decrease in the power of the engine caused by a disturbed ratio in the fuel-air mixture, which is far from optimal. In this case, knowing that you replaced the carburetor, it could be a bad setting of the H-needle, insufficient fuel supply, air leaks.

Is your chainsaw still as easy to start as it used to be?

If the saw is at idle and you put it against a piece of wood, as if you were trying to cut it, can you hear the rpm change?

I know you changed the filters, but can you check the fuel line that supplies fuel to the carburetor? For example, you can disconnect it from the carburetor, connect a syringe to it and try to suck the fuel and see if there is a problem with it.

You can also pay attention to the impulse line. This is the pipe that is connected at the top of the carburetor and goes through the baffle towards the cylinder. To see if there's a problem with it behind the baffle or its connection to the crankcase you'd probably have to remove the top cylinder cover.

 

[Old2stroke]

The second video (tinman) is excellent. The first one gives good info on setting low speed operation but is totally useless on how to set the high speed needle (the most important one) and even gives a false impression of what it does.

 

[Sidecarflip]

If a loop is correctly sharpened and the rakers set correctly, the loop will self feed into the wood with no additional pressure applied to the saw. Something I never do is apply additional pressure to the saw to enhance the cut. I always let the saw feed itself, I never force it.

 

[LuDookie]

@LuDookie I am was just using it as I used to do. It chain stop running and I and removing it from wood and try again.

If you get the tuning figured out, try running the saw through the log without using the dogs, and using it as a lever. Nurse it. That’ll even help you tune it.