What are the signs of overheating & scoring?

[THALL10326]

I've heard peolple advise to get rid of the muffler screen entirely. I would think that this would allow debris to get down into the muffler. Is this a bad idea?

Yup its a bad idea. Those screens are really spark arrestors. Run a saw at nite without the screen in the muffler and your see sparks coming out the muffler. In a real dry forrest those sparks could set off a blaze, not likely but possible. Thats why they putem in there, better to be safe than sorry..

 

[sugarbush]

Thanks guys. The saw is a 2006 I got around August, she's only seen maybe a gallon of premix so far.

I was running at 40:1 using the Stihl Super (synthetic blend?) oil but now I'm back to 50:1 in 89 octane with stabilizer, though the gas is never more than 1 or 2 months old.

The mechanic at my dealer said she's running right. Not too rich, not too much oil from what he could see. I don't know whether he put a tach on her.

I cut with her tonight, she's a HOSS again!

Do you cut full throttle?

 

[THALL10326]

Do you cut full throttle?

Good point there Sugar. I'd bet 90% of all muffler screens clogged in weed trimmers come from running them at partial throttle. Your as sharp as a tack Sugar!!!

 

[sugarbush]

Good point there Sugar. I'd bet 90% of all muffler screens clogged in weed trimmers come from running them at partial throttle. Your as sharp as a tack Sugar!!!

confuscis said : even a blind hog find's an acorn once in awhile.

 

[THALL10326]

confuscis said : even a blind hog find's an acorn once in awhile.

Yeah right, I know how you old timers are, yaw know all the little secrets, thats why I respect age so much, it brings with it lots of wisdom and you got plenty Sugar, we all know that. You don't fool me any, you slick sucker you,wink.

 

[sugarbush]

But the older i git the harder it is to remember those secret's.

 

[THALL10326]

But the older i git the harder it is to remember those secret's.

Sure, we know,LOL

 

[bwalker]

When I used screens in my saw's mufflers I never had one plug up when using a 32:1 ratio. I have a Stihl FS-85 trimmer that has never had the spark screen removed and has been used commercially for some time (over 500 hours at the least) at 32:1. Runs like it did when new. Its also been used with a brush blade quite a bit, which causes any trimmer to run quit rich due to the loads involved.
Me thinks something else is going on with this saw. Especially since the issue happened within a few gallons of fuel and the oil used was of fair quality. I do'nt care how rich the saw is it would'nt plug up this fast.

 

[sugarbush]

thall,you start the monster yet?

 

[sugarbush]

may not be running it hard enough (hot enough) to keep the screen clean.

 

[bwalker]

may not be running it hard enough (hot enough) to keep the screen clean

I do'nt understand how anyone can run a saw in this way.
Is it possible that the dealer made up the spark screen story as a way of explaining a problem which he could not diagnose?

 

[sugarbush]

I do'nt understand how anyone can run a saw in this way.
Is it possible that the dealer made up the spark screen story as a way of explaining a problem which he could not diagnose?

I've never seen one plug up that soon, and i suppose the dealer could be making it up but what could he be covering up? Don't think a heavy mix would have that affect that soon. but rereading his post it sounds like he was worried about (hurting) the saw, letting it cool down between cut's and maby short cut's. the only thing i can think of is not running the saw hot enough.

 

[bwalker]

but what could he be covering up?

I dont think the dealer is covering up anything, maybe he was just trying to save face instead of saying he couldnt explain what the heck was going on.

 

[Lakeside53]

I rarely see a plugged screen in medium-> larger saws. I see them in blowers and weed eaters - primary cause - not running at full throttle. Oil mix ratio (within reason) really won't affect the screen.

Are you cutting decent wood or just limbing?

The 361 screen is very large... doesn't affect performance and as for blockage - I've popped out maybe a 100 in the past year and never seen any blockages of any type, and rarely even a dirty screen...the 361 muffler runs very hot.

Take off your muffler and check the piston/cylinder and exhaust port for carbon buildup. Unlikely it would be just in the screen.

Definitely tach the saw (i.e., not by "ear"), and check it often to see it it's getting richer - you should be able to hear it anyhow. 13,500-14k is typcail WOT with a medum bar.

The factory setting (you said you never touched it) is pretty lean... Keep an eye on it and take it back to the dealer if there is any question...

 

[Lakeside53]

I do'nt understand how anyone can run a saw in this way.

Limbing and thining - small stuff... Just blips of the throttle.. can do it. Over a long period.

 

[adkranger]

Bad idea

I've heard peolple advise to get rid of the muffler screen entirely. I would think that this would allow debris to get down into the muffler. Is this a bad idea?

If saw is maintained properly and screen/muffler checked occaisionally the spark arrestor screen should have no effect on performance. If you happen to cause a wildfire because you removed the screen on your saw, guess who pays for all suppression costs incurred? You may also, and probably will be assessed additional fines in court as well. The Feds and many states are aggressively prosecuting these cases in recent years, not just arsons but negligent and careless fire starters as well. Don't ask me how I know this....

Now if the saw is not primarily used in the woods/bush, go ahead do want you will with it. But if used in the woods, leave that protection in place. My .02.

Oh, and I agree with the others, this seems wierd to me. For the screen to be clogged so early in it's service life. I've got two saws, 036 & 028, that I've never had to clean the arrestors, inspected them but never had to clean. Many, many, countless tank fulls of 50:1 Stihl mix through them over many years.

 

[tek9tim]

Good word on the spark arrestors, ADK. We all know that actual contact of the muffler to material is much much more likely to start a fire, but if you don't have a screen, they will hang you for it. And fires aren't cheap.

 

[Canyon Angler]

Wow, I really opened Pandora's Box here, didn't I?

1. Dealer showed me the screen. It was plugged. I've since inspected it, and it's no longer plugged. When I took the saw to him it ran like crap. Now it runs like a champ. I can't imagine the dealer "making up" the plugged screen story...what does he have to hide? And if that wasn't the reason for the saw running bad, why would he hide the real reason? Maybe I'm just too trusting and should join the KGB...

2. Under load, I use 100% throttle 90% of the time. However, I have also allowed the saw to idle a lot to a) let it cool between cuts and b) allow the motor to break in under a variety of loads and throttle positions. As I mentioned, it's a new saw. Perhaps all the idling helped to cause the carbon fouling. I dunno. Maybe it's the 40:1 mix. I dunno. Maybe it's a plot by Husky and Dolmar to discredit Stihl and conquer the world. I dunno. But I do know I'll check the screen again. YMMV.

Thanks again for all the help.

Jeff

 

[Kneejerk Bombas]

I suspect when an exhaust screen clogs, it's a fairly fast event. As the exhaust flow is restricted, the saw runs richer, which causes it to clog more.
The 361 meets emission standards, like many other modern saws, by restricting the exhaust. By restricting the flow, the exhaust stops a lot of unburned fuel from spilling out into the atmosphere.
This restricted flow, my guess is, would increase the likelihood of a clogged screen.
Pay attention to carb settings, do visual inspections of the screen frequently, and avoid partial throttle operation.

 

[sugarbush]

you started something very interesting, i don't think anyone has seen that happen in that new of a saw before. even when you think you've seen about everything with a saw, it git's the juice's flowing when something like this come's up. ( at least for me ) would you explain a little better on your cutting method before this problem?