Problem with a Stihl

[Superman]

Stihl MS-180C. Starts fine. Runs fine for a bit. Then, it starts to act strangely. It will go into a mode where it runs fine at idle and half-throttle, but bogs down if you give it more than half-throttle. Then, it might return to completely normal. Other times, it will idle way too high and not bog down at full throttle. Then, it might return to completely normal again. I've cleaned (and removed, actually) the spark arrester screen, the air cleaner is clean and I've replaced the fuel pickup (fuel filter) twice.

I'm tempted to get the manual and start a dissection of the fuel system. The carburetor does not have an adjustable mixture. Only the idle speed can be adjusted. I wonder if there might be a pinhole in the fuel line, or something wrong with the fuel pump/diaphragm system. I know nothing about the diaphragm/fuel pump thingie.

[oldE]

Supe,

Check the choke linkage. Also check the throttle butterfly to be sure it is not coming loose.

Good luck.
Les

[Superman]

Thanks, Les. I will check those. Even though the saw always starts fine, and always runs fine for a bit.

[Gretch]

The ethanol crap they put in gas destroys the rubber fuel lines in these things. I have 4 saws and have had to do surgery on 3 of them for the same thing. Often the hose is cracked right where it leaves the tank and heads up to the carb. I think that is because it gets a combination of heat soak and ****ty fuel.

Yours sounds like it is sucking air...... especially at full throttle. Once you check out your fuel line I also recommend you use Startron in your mix...... it may save your saw from going lean because of the H2O the ethanol attracts.

A lot of guys up here have had saws destroyed because of this ethanol garbage......... two stroke sleds, too!

[rick-l]

Here is how those carbs that work upside down function. Very fascinating and critical to understand what is wrong.

Like how the primer just fills the carb with gas, it doesn't put anything into the intake. How all those tygon fuel lines have to be airtight.

http://wem.walbro.com/distributors/servicemanuals/WTseries.pdf

[pete3799]

+ 1 on the crappy fuel.
You should have a high speed (H) and a low speed (L) jet.
At idle adjust L so it's half way between where the motor starts to break up.
Reset idle.
Adjust H at wide open throttle ( clamp the bar in a vise) till it revs the highest.

[rouxroux]

Originally Posted by Gretch

The ethanol crap they put in gas destroys the rubber fuel lines in these things. I have 4 saws and have had to do surgery on 3 of them for the same thing. Often the hose is cracked right where it leaves the tank and heads up to the carb. I think that is because it gets a combination of heat soak and ****ty fuel.

Yours sounds like it is sucking air...... especially at full throttle. Once you check out your fuel line I also recommend you use Startron in your mix...... it may save your saw from going lean because of the H2O the ethanol attracts.

A lot of guys up here have had saws destroyed because of this ethanol garbage......... two stroke sleds, too!

+1 We have a Stihl "Multitool" and now add the Sta-Bil Marine formula to counteract the ethanol crap. Our dealer says that ethanol-related repairs make up 75% of the problems they are repairing.

[pwd72s]

Find a source for racing gas or gas without alcohol. Maybe marinas there sell it?

[Superman]

You guys are the best. I'm going to come here for all my advice, regardless of topic.

Now, as long as you guys are here, I've been having trouble with my girlfriend. The problem is, she makes a LOT of noise when we do the Wild Thing. Is there any sort of muffler I can use....?

[rusnak]

Use your member of Congress for that.

+1 on the intake leak as the chainsaw problem.

[KFC911]

Originally Posted by Superman

.... The problem is, she makes a LOT of noise when we do the Wild Thing. Is there any sort of muffler I can use....?

Just like the Stihl, this sounds like a typical ethanol problem also...either too much or not enough, I'm not sure which. You should research this extensively

[DanielDudley]

There is also a screen to filter gas in the carb that can gum up, and then there can be blocked air filters.

[JJ 911SC]

Originally Posted by pete3799

+ 1 on the crappy fuel.
You should have a high speed (H) and a low speed (L) jet.
At idle adjust L so it's half way between where the motor starts to break up.
Reset idle.
Adjust H at wide open throttle ( clamp the bar in a vise) till it revs the highest.

I got the same problem with one of their blower...

Not sure if its normal but my L & H adjust screw seem to be only turning 1/4 turn?

My mix seem pretty dark so for a change, I read the instruction on the oil little container from Stihl and it mentioned 50:1 ratio and using 89 gas.

I'm using 87 and I might have been using 40:1 (Sear chainsaw mix if I remember)

[s_morrison57]

Should'a bought a Husky - wouldn't have had a problem

[Joeaksa]

Buy gas from a marina. They usually have fuel without the ethanol. This crap wrecks everything, especially boats where fuel sits in them for long time periods.

[Dantilla]

My yard equipment gets 100LL Avgas. No alcohol, and far more stable than car gas. My local airport has a self-serve pump where I get a few gallons at a time.

[Normy]

Interesting thread. I have a 14 inch Homelite saw [model UT10540] that from the side looks very similar to that Stihl, and it has been giving me fits. Hard to start, and when it does start, it wont idle below half throttle. I'm pretty sure it is running a bit lean.

Interesting thoughts on the ethanol fuel; time to head over to the marina!

I flew RC model airplanes for years, and got pretty good at adjusting the carburators to run correctly on their glow engines. I went to do this on the Homelite, and discovered that it requires some sort of special tool- the H and L adjustments require a tool that is cylindrical but with one single tooth on one side. Anyone know if this tool is available?

N

[KFC911]

Originally Posted by s_morrison57

Should'a bought a Husky - wouldn't have had a problem

Husky's are great, but not immune to ethanol issues either. Just a caveat for those that can't access Marina/100 LL, (non-ethanol) gas...it doesn't hurt to "run" ethanol in these things...just don't let 'em sit with "drunken gas" in the tanks!!!

[JJ 911SC]

Originally Posted by Normy

... I went to do this on the Homelite, and discovered that it requires some sort of special special tool- the H and L adjustments require a tool that is cylindrical but with one single tooth on one side. Anyone know if this tool is available?

N

By looking at the adjustment screws on the Stilh, I think the same applies

[Superman]

I went to the Stihl store, and became even more confused. They told me never to run gas that is higher octane than 87. They said it will score the cylinder. I'm going to check the manual on that one. They said to use only synthetic oil (Stihl brand, of course).

They also had a fuel line in stock and it was only $4.50 with tax. There is a YouTube video showing exactly how to replace this line, so I will do that. I hope I can get it running good soon, as it has its job cut out for it, so to speak. Several downed fir trees I need to slice and dice. I want to avoid taking it to the Stihl mechanic. The repair bill could be half the price of a new MS-180C. I would hate that.