Stihl MS181 idles but will not rev

[thumper71]

I have a Stihl MS181. I only has about 10 hours total on it. It was running great when I put it up. A couple of weeks later I started it up. I idled great and seemed fine. However, it will not rev up. Pull the throttle and it bogs and dies. I have tried all the basics, gas, fuel filter, fuel, plug, carb, air filter, hoses.... Plug is new and looks great and appears to be burning clean and properly. If I cover the carb air inlet with my thumb and throttle up it will pick up RPM's and rev up and run OK but not well. As long as the intake is covered it runs ok. Uncover it and it's back to the same problem.

 

[HD2010]

Not sure what you have done to carb but take carb apart clean well. If that don't work try adjusting metering valve a little. I bent tab for valve up just a little and saw works great now. I posted same problem with an 018C.

 

[jus2fat]

The Stihl 181 is a fairly new model...is it still under warranty..??

If so..take it back to the dealer for warranty covered repairs.
With only 10 hours on it...could be a factory defect problem.

You did drain the old gas/oil mix and run it dry before putting it up..right..??

And you are running a new mix now...fresh gas and oil mix...right..??

J2F

 

[thumper71]

I have tried the suggestions y'all have given me. I use it very little and it is out of warranty. I do put it up dry and am using new fuel and have not used fuel with ethanol in it in the saw. Still have the same problem. I did notice that there seems to be a lot of carbon on and around the muffler. Could this be the problem? If so, what is the problem and how would I solve it.

 

[thumper71]

Problem Solved

I removed the muffler. Problem Solved. The muffler was plugged with carbon gunk. Saw runs great..Thanks to all for making me think a little harder.

 

[dboyd351]

Maybe check the spark arrestor screen to see if it is clogged with carbon? Fuel filter or fuel line blocked? Air leak in the intake? Bad diaphram or plugged screen in the carb? Any of those could do it.

Since blocking off the air intake seems to make it run a little better, maybe you should start by looking for leaks in the air intake. If the spacer between the carb and the cylinder has a crack in it, or the machine screws holding it aren't tight, it will suck air instead of a proper fuel/air mix, and it won't rev worth a crap.

 

[blsnelling]

As mentioned, pull the carb apart and clean it.

 

[ZeroJunk]

Hopefully you can get the dealer to fix it under warranty. He will most likely replace the carb. Those fixed jet carbs are a pain or impossible to clean without taking the plugs out.

 

[Duke Thieroff]

How come no one has suggested to richen up the L needle a bit?

Tear the whole saw apart looking for the issue, but not turn a screw out a quarter turn?



Chris

 

[HD2010]

How come no one has suggested to richen up the L needle a bit?

Tear the whole saw apart looking for the issue, but not turn a screw out a quarter turn?



Chris

Because these saws only have an idle adjustment. There is no high or low adjustments.

 

[ZeroJunk]

Because these saws only have an idle adjustment. There is no high or low adjustments.

And, these carbs are just a problem. The small displacement weedeaters, blowers, and saws that use them need such a small orifice that a tiny speck will stop it up. You can't just pull the needles and blow cleaner through them like the older models.

 

[Duke Thieroff]

Well that stinks. My apologies.


Chris

 

[thumper71]

Problem Solved

Maybe check the spark arrestor screen to see if it is clogged with carbon? Fuel filter or fuel line blocked? Air leak in the intake? Bad diaphram or plugged screen in the carb? Any of those could do it.

Since blocking off the air intake seems to make it run a little better, maybe you should start by looking for leaks in the air intake. If the spacer between the carb and the cylinder has a crack in it, or the machine screws holding it aren't tight, it will suck air instead of a proper fuel/air mix, and it won't rev worth a crap.

I got to thinking...an engine is an air pump. I was so focused on the intake I was ignoring the exhaust. Free flowing air makes for a good running engine.


The spark arrestor was plugged up and the muffler was gummed up as well. Cleaned both and the saw runs great.

Thanks!

 

[bobt]

My Dad's neighbor had the same problem with his 170 or perhaps it was a 180. It would start and idle just fine, but wouldn't take the throttle.

He said he put a kit in the carb, but it still didn't run.

I offered to see if i could do anything with it, so I removed the carb, checked if he had the diaphrams and gaskets in the right order (They were ok), and sprayed carb cleaner through it. All to no avail.

For the heck of it, I called the Stihl dealer and he said that he had already told the guy that he needed a new carb, as the tiny high speed passages were plugged. He said the guy threw a fit, and walked out. He said that a new carb was somewhere around $25.00, and he offered to install it for nothing.

What a cheapscate that guy was!

I think when all is said and done, a new carb will be required in order to get your saw running again.

Bob