Stihl MS250 is possessed!

[Cliff R]

My neighbor gave me his near mint condition MS250. His wife bought it for him new about 4 years ago. In all that time it's cut about half a cord of wood and trimmed up a few down limbs on his property.

He's had it over here half a dozen times for me to look at it, and back to the dealer once, who told him it needed a new carburetor.

Every time I've had it over hear, it's required a slight "tweak" to the carb, I dump out his old fuel, it runs flawlessly, and off he goes with it.

This last trip he says to keep the saw and he never wants to see it again. I drained the old gas from it, and it fired right up. Once again just a tad out of adjustment, but very close. I had some down trees from a recent storm so ran two full tanks thru the saw....flawless.

A month goes by, I get it out, starts right up, idles a little funny, dies out. Starts right back up, idles OK for a minute or two, dies out. I didn't have time that day to do anything with it, so I grabbed one of my 55's instead and completed the job.

Another couple weeks go by and yesterday I pull it out to see what's going on. It's down about 2" in the tank so I fill it up. Fires right up, and ran flawlessly thru the entire tank, never had to touch the carb or anything else.

Just looking for some ideas from anyone with experience with this model to find out what's going on? Vent issue? Fuel line? Dirt floating around in the carb? It doesn't act like it's got any air leaks anyplace, because when it does run, it runs right thru the entire tank and never grumbles once. The problems both of us were seeing, is that some days when first started up, it woln't stay running at idle and has required numerous very slight carburetor adjustments to get it back in tune......Cliff

 

[H 2 H]

If the saw has had bad fuel in it for a period of time I would clean the carb first

Have either of the fuel line or filter ever been changed; lines might be getting soft IMO

 

[RandyMac]

ditch it, buy an Echo. :hmm3grin2orange:

 

[SawTroll]

If the saw has had bad fuel in it for a period of time I would clean the carb first

Have either of the fuel line or filter ever been changed; lines might be getting soft IMO

There always seem to be issues with those saws.....opcorn:

ditch it, buy an Echo. :hmm3grin2orange:

I'd keep even a MS250, if Echo was the only option.....:msp_rolleyes:

 

[H 2 H]

With the fuel we have today (in the US) four years is along time for fuel line IMO :biggrin:

Maybe that's why they say to change the lines every 2 years

 

[Fish]

Inspect the top ofthe fuel line, between the tank and carb, look closely while you flex the tubing, they are notorious for tiny cracks there, also
pinch together the fuel line where it sits immersed in the fuel, it can get soft and gummy.

I did have one that I called haunted once, would run great when I would test it, the guy would eventually bring it back as it would stop
on him after using it for an hour or so. Finally cured it with another coil.

 

[Cliff R]

Coil seems to be fine, starts, runs, restarts fine, even when it's acting up. The stalling out at idle issue has lean related symptoms. When this thing runs, it runs thru an entire tank with zero issues. When it decides to act up, it stalls out at idle.

I'll pull the fuel line and replace it, that sounds like a good place to start....thanks....Cliff

 

[biggus]

Is the idle speed set just a tad on the low side? My new out of the box 290 was set by the dealer to that magical place where it was idling like a cadillac which sounded good but would occasionally stall out after a load. Maybe just bump it up a bit?

 

[old-cat]

There always seem to be issues with those saws.....opcorn:

I've never had a lick of any problem with mine, and I beat the crap out of it. Many kickbacks, twisting the bar, trees falling back on my cut, yanking the stuck saw, everything possible to beat that thing up!

 

[Cliff R]

"Is the idle speed set just a tad on the low side?"

I never have to touch the idle speed for most outings. When it does act up, it speeds up at idle, leans out, and stalls. Increasing the idle speed changes nothing, it still stalls out at idle. It will continue to do this no matter how many times it's restarted. I even loosend the fuel cap to make sure it wasn't a venting issue, no change.

After the last acting up deal, I tossed it on the workbench and left it there several days. Came back to it, topped off the tank, it fired right up and ran flawlessly thru the entire tank without touching any adjustments.

I'm slowly finding out why it was given to me. I'm sure the previous owner got tired of not being able to count on it....Cliff

 

[rmh3481]

Hi Cliff,
Walbro WT-215? May be an intermittent leaking mechanical check valve in the carb's high speed nozzle. You can test the nozzle with a piece of fuel line and some vacuum. What happens is air leaks back into the metering circuit through the check valve and idle is usually where it shows up. This may also be why the dealer said it needed a carb.

Walbro service manual, pages 15-17 shows the tests.
http://wem.walbro.com/distributors/servicemanuals/ServiceManual.pdf

If it turns out to be the nozzle the part number is 86-583-1. ($2)

 

[Cliff R]

Good info! I'm not sure what carb it is using, but when I get time I'll tear into it and see what's going on.

I'm not surprised our local dealer recommended a carburetor replacement. Their capabilities over there are quite limited, they troubleshoot by changing major components. Everyone who's ever brought their Stihl here after going to the dealer says that the dealer recommended to replace the saw instead of fixing it, and they estimate to fix it was nearly the cost of a new saw anyhow.....Cliff

 

[w8ye]

The best Stihl dealer tha actually stocks parts in these parts is M & M on the North edge of Ashland.

 

[50blues]

When it leans out and dies how full is the fuel tank? Have you ever had a straw with a hole in it? It works fine as long as the liquid is above the hole. Once the hole is exposed it sucks air and wont work. Try a new fuel line. They are cheap and easy to replace.

 

[Cliff R]

The tank level doesn't seem to matter. Right now since I started the thread is not behaving badly, and went thru several tanks without a grumble. I'm talking good about it so it will act up again!

When it does run like it's supposed to, it's a decent little saw, good power for the cc's. Pretty much maxxed out with a 16" bar when you get into heavier material, but makes a great limbing saw. It's got more chain speed than my CS-370's, doesn't share quite as broad of a power curve. I'll bet it would really shine with a 16" bar and 3/8LP......Cliff

 

[Saw Dr.]

Good info! I'm not sure what carb it is using, but when I get time I'll tear into it and see what's going on.

I'm not surprised our local dealer recommended a carburetor replacement. Their capabilities over there are quite limited, they troubleshoot by changing major components. Everyone who's ever brought their Stihl here after going to the dealer says that the dealer recommended to replace the saw instead of fixing it, and they estimate to fix it was nearly the cost of a new saw anyhow.....Cliff

In defense of the dealer, we hardly do any carb work anymore. With Stihl owning Zama, the carbs are just too affordable not to replace them. At $65/hr plus $15 for the carb kit, who wants to fool with running them through the USC when you can bolt a new one on for $30 in many cases.

I would check the fuel and impulse lines . I have seen more than one 1123 series that was twisted out of a cut and broke or pulled off the impulse line. Once they get to be about 7+ years old, the crank seals start to get hard. This actually seems to be based more on age than the hours on the saw. Press/vac check is probably in order sometime when it is acting up.

 

[dsell]

In defense of the dealer, we hardly do any carb work anymore. With Stihl owning Zama, the carbs are just too affordable not to replace them. At $65/hr plus $15 for the carb kit, who wants to fool with running them through the USC when you can bolt a new one on for $30 in many cases.

I would check the fuel and impulse lines . I have seen more than one 1123 series that was twisted out of a cut and broke or pulled off the impulse line. Once they get to be about 7+ years old, the crank seals start to get hard. This actually seems to be based more on age than the hours on the saw. Press/vac check is probably in order sometime when it is acting up.

Crank seals already? A friend is bringing me a 250 this week. He bought it new, probably 7 or 8 years ago. He cuts firewood every winter with it just like I do with my saws. He is always complaining about how tempermental this saw is. Last year, I put on a new fuel line/ filter and it ran fine for me. I told him I will probably have to kit the carb. , check spark and compression. Can I pressure test the seals or does it have to be vacuum? What pressure or vacuum should it hold and for how long?