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More Problems With My Stihl MS170

Started by Bigfoot870, October 19, 2016, 07:22:34 AM

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Bigfoot870

After having a new fuel tank (with fuel line & filter), installed in the spring, under warranty, it worked fine.  Then, I didn't use it for 3 1/2 months.

In Aug & Sept, I had some horse logging done, and decided to use the wood that was left on the landing for fence posts. I'm simply cleaning off the, and junking the 3" to 5" dia red spruce at 6 feet (not sharpening). I started last week, and the saw worked fine, but seemed to be idling fast (the idle was adjusted by the Stihl tech, back in the spring). Yesterday, it started to idle faster, so I adjusted the screw, but it didn't change a thing. Since new, there has been a black sludge seeping out underneath the muffler, and it's getting worse (FYI - the muffler screws are not loose). I took the muffler off, back in the spring, to find that there is no gasket. Could this be part of the problem ?

Also, I am considering installing a Walbro WT-215 carb. Is my only mod to drill holes in the plastic, to access the H & L screws? (I never would have bought this saw, had I known the carb was not adjustable. My buddy's Echo CS-310 is totally free of issues.)

Thanks Guys :)

joe_indi

Black sludge below the muffler is possibly from residual 2 stroke oil, maybe from using with throttle only partially open, or too much oil, or wrong oil.But, it could also be chain oil splashing on the body.
The single screw on the carb controls the richness/leanness of the idle and a bit of above by increasing the air, not the fuel. You turn that screw clockwise, it is actually moving out, increasing the air and increasing the idle speed.
Turn the screw anti-clockwise, you are turning in the screw to decrease air, make the idle mixture richer and the idle speed lower.
Turn the screw anticlockwise to its stop. Turn it two turns clockwise , start up the saw and warm it. Now, if the idle seems too fast turn the screw anticlockwise to slow it down or clockwise if you want to increase the idle speed.
If the idle speed increases only when the saw is hot, I would check the pickup body in the fuel tank, for partial blockage. I would also check the four screws at the bottom, the ones that hold the cylinder and engine pan together.
I would also check the metering level in the carb because this fast idle when hot that you mentioned could also be due to a low metering level, but I would leave that as the final step.
In case you have a mesh screen on the muffler make sure it is not blocked. This too could increase idle speed.

Bigfoot870

Thanks Joe......

Black sludge below the muffler is possibly from residual 2 stroke oil, maybe from using with throttle only partially open, or too much oil, or wrong oil. It's none of these.

But, it could also be chain oil splashing on the body. Maybe.

The single screw on the carb controls the richness/leanness of the idle and a bit of above by increasing the air, not the fuel. You turn that screw clockwise, it is actually moving out, increasing the air and increasing the idle speed.
Turn the screw anti-clockwise, you are turning in the screw to decrease air, make the idle mixture richer and the idle speed lower.
Turn the screw anticlockwise to its stop. Turn it two turns clockwise , start up the saw and warm it. Now, if the idle seems too fast turn the screw anticlockwise to slow it down or clockwise if you want to increase the idle speed. I went counter clockwise, as per the markings on the saw, to no avail.

If the idle speed increases only when the saw is hot, I would check the pickup body in the fuel tank, for partial blockage. It idles fast right from a cold start. The fuel filter / pick up is new and clean.

I would also check the four screws at the bottom, the ones that hold the cylinder and engine pan together. I will, thanks :)

I would also check the metering level in the carb because this fast idle when hot that you mentioned could also be due to a low metering level, but I would leave that as the final step. The saw works great, when revved up, so would this still apply? What about the Walbro WT-215 fitment?


In case you have a mesh screen on the muffler make sure it is not blocked. It's fine.
This too could increase idle speed.

joe_indi

Since your saw is not too old I did not mention another possibility, the oil seals. If you have the fast idle even from cold, it could be the seals.
But before that check a simple possibility like a carb throttle butterfly that does not close properly.
The Walbro WT-215 carb is for the 210 - 250 saws. Whether the venturi diameter matches I cannot say offhand.
But I can check tomorrow and let you know.
But, a carb swap option at this point might not be the right solution. The cause for the fast idle has to be found first.
BTW, when you blip the throttle is there any hesitation, a slight leaning out before revving? Or is the revving ok?

Bigfoot870

She revs just fine Joe, with no hesitation :)

ladylake

 A Echo CS352 with good tuning and a muff modd is a real nice saw, really good power for 33c.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Bigfoot870

Quote from: ladylake on October 19, 2016, 07:03:57 PM
A Echo CS352 with good tuning and a muff modd is a real nice saw, really good power for 33c.  Steve

Please know that if I could afford a different saw, I would not be troubleshooting!!!!

joe_indi

It's starting to look more like a mechanical issue, such as a not fully closed throttle valve. Maybe the throttle rod is a bit bent, or like I mentioned earlier the throttle valve needs to be aligned.

Bigfoot870

Thanks Joe, I'll check for that.

I'm going to clean the carb, and install a carb kit.

Also, I'll check the bolts to make sure I don't have an engine leak.

HuckFin

My Stihl MS180 has the black sludge problem too but idles where it should be, at least up until it fouls the sparkplug out from flooding. I just bought a new $10.95 (including shipping) carb on ebay for it, when it gets here I will see how it works out.  Also I did not know the single idle screw also adjusted the air/fuel ratio, thanks joe_indi. So I will play with that before I put on the new carb.

Bigfoot870

I just pulled the muffler off, and I have a bad leak between the head and muffler (the nuts were not loose). This has clearly caused the black sludge. I'm going to add a gasket, even though there was none from factory.

Could this have caused the fast idle??

I'm going to clean the carb, and add a kit anyways.

The spark arrestor screen is sooty, but by no means blocked. I'll give it a good cleaning.

Texas-Jim

Its unlikely an exhaust leak would cause a idle problem. Check the shafts in carb and see if they are loose, it could be pulling air. Heck a brand new carb from stihl is only 28 bucks. I never rebuild them for customers, by time kit and labor figure in a new carb is cheaper.
What we do in life echoes through eternity.

Bigfoot870

I installed the carb kit myself. Thanks anyways.

joe_indi

I checked my 180 with the muffler removed.
My saw has not seen much use since it was cleaned up. But look at that sludge!
I cleaned it up and fitted an exhaust gasket.
If there is an exhaust leak, the cylinder/engine pan joint would be affected if it is heated (by the exhaust) beyond a point




Bigfoot870

Thanks Joe. My gasket should arrive Tue or Wed :)

Bigfoot870

You are right Joe, the screw actually has a left hand thread :)

I started with two turns, as you advised, and it was very fast. I gradually went back to about one full turn, and it starts easily, revs great at full throttle, with only a small hesitation (don't forget, I am used to pro saws). The idle is still a bit fast for my liking, but the chain is nowhere's near turning on it's own, with proper chain tension, so I'm leaving it alone.

Thanks again Joe :)

Quote from: Bigfoot870 on October 19, 2016, 01:30:42 PM
Thanks Joe......

Black sludge below the muffler is possibly from residual 2 stroke oil, maybe from using with throttle only partially open, or too much oil, or wrong oil. It's none of these.

But, it could also be chain oil splashing on the body. Maybe.

The single screw on the carb controls the richness/leanness of the idle and a bit of above by increasing the air, not the fuel. You turn that screw clockwise, it is actually moving out, increasing the air and increasing the idle speed.
Turn the screw anti-clockwise, you are turning in the screw to decrease air, make the idle mixture richer and the idle speed lower.
Turn the screw anticlockwise to its stop. Turn it two turns clockwise , start up the saw and warm it. Now, if the idle seems too fast turn the screw anticlockwise to slow it down or clockwise if you want to increase the idle speed. I went counter clockwise, as per the markings on the saw, to no avail.

If the idle speed increases only when the saw is hot, I would check the pickup body in the fuel tank, for partial blockage. It idles fast right from a cold start. The fuel filter / pick up is new and clean.

I would also check the four screws at the bottom, the ones that hold the cylinder and engine pan together. I will, thanks :)

I would also check the metering level in the carb because this fast idle when hot that you mentioned could also be due to a low metering level, but I would leave that as the final step. The saw works great, when revved up, so would this still apply? What about the Walbro WT-215 fitment?


In case you have a mesh screen on the muffler make sure it is not blocked. It's fine.
This too could increase idle speed.

Bigfoot870

Joe,

With the idle adjustment screw set "down" so that the saw does not actually stall, the idle is still quite fast.

I used the saw a bit yesterday, and it performs perfectly (with a clean muffler screen and a fresh carb kit).

Should I be looking at the gasket between the head and base? Should I be looking at the crank seals?

Also, I see aftermarket gaskets for between the carb and the airbox (or head, but I doubt it due to the boot and o-ring seal design), online. There is no gasket from factory. Should I add a gasket between the carb and airbox?

Thanks :)


joe_indi

Start up the saw and warm it up. Turn the carb screw (clockwise) till the clutch engages and the chain starts to spin. Now back off the screw (anti clockwise) till the chain stops turning. Back off a further half turn from that point. How is it after doing all this? If you have a tachometer you could also get the reading at idle.

Bigfoot870

I've already done this Joe, and there is a fine line between too fast and stall. I don't have an RPM meter.

joe_indi

If you are up to it, bend the metering lever upwards just a bit and see it things improve. If it does, bend it a little more so that the rpm drops enough for you to adjust the screw to get an increase in rpm. But keep checking the open throttle revs in the cut as you stand the risk of making the carb over rich.

Bigfoot870

Joe,

It was level with the machined face of the carb, when I installed it. I'm afraid that I might not have the patience to pull the carb off and open it up, what could be multiple times, to get the "correct" adjustment. Is there anything else I can try first?

Thanks.........

joe_indi

A tiny bit above that level is fine. Did you check if the throttle butterfly is closing completely?

Canadiana

Thanks for the excellent read gentlemen
The saw is more fun than the purpose of the wood... the forest is trembling 🌳

Bigfoot870

You are more than welcome Canadiana:)

I have installed the muffler gasket for an MS250, and it fits perfectly. I have also installed a new spark arrestor screen.

I had to travel to a different Stihl dealer, than where I bought the saw & had warranty work done, to buy the screen. The technician there thinks that the exhaust leak might effect performance, due to diminished back pressure......

I will try the saw before going back into the carb.

The tech at my regular Stihl shop says that the idle should be 2800 RPM, and basically said that if a properly tensioned chain isn't turning, I should be good. He said that the bigger pro saws that I used in the past, likely idled around 1800 rpm......



Quote from: Canadiana on October 26, 2016, 12:24:35 AM
Thanks for the excellent read gentlemen

Bigfoot870

The pros use a propane torch to get the spark arrestor screen red hot, then when it cools, the carbon is almost white, and comes off by tapping it.

I put my screen on the red hot coals, in my airtight wood stove, for about three minutes, and once it cooled, the remaining carbon came right off with a small wire brush.

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