# Stihl MS250- Won't Start(Thread# 9,384)



## bigv (Nov 23, 2012)

Howdy, Gentlemen:

Two years ago I purchased a Stihl MS250, used. It ran well the first year. Next year I had issues with it not wanting to start. I determined I was getting spark, so I disassembled the carburetor completely, and then used carb cleaner to clean out all the small passages in the carb. I used the Carb Cleaner's plastic straw to run pressurized cleaner through each and every passage. 

I reassembled the carb, put the saw back together and ran it all of last winter. 

I went to crank it in October(it was last used in April or May of this year). I drained out all of the old fuel, put new fuel in. Well, I pulled over on it cold start and it started and just barely ran for a few seconds and then shutoff. 

Then, no matter what setting it was on, it seemed like it was flooding the saw's cylinder. I again pulled the carb, went through it, and reinstalled it. Still would not pop off in cold start or any other setting. 

I checked the coil gap with a business card, cleaned the coil and connections, and reinstalled. I have even sourced another carb from Robsterdog on Ebay and tried installing it. 

Just again tonight, I did the following:

Had let the saw sit for several hours, cleared it out via cranking without spark plug. Installed new spark plug, turned off all lights and then pulled over while grounding the saw. Saw the light from the spark, not brilliant lightning or anything, just a spark mind you. I got some scotchbrite and cleaned the coil, cleaned the flywheel surface with that. I then put everything back together. 

I have the carb from Robsterdog installed- he has a good reputation and stated it was a good carb. 

I put the saw in full choke setting, pulled twice on the handle with great force. No sound of ignition or popping off. Put saw on fast idle, tried one pull, no ignition, nada bupkiss. I tried it on the "run" position several pulls and still got nothing. 

Let the saw clear out, removed plug to make sure it was cleared out by pulling over on it, and let it sit in a warm area of my garage for a few hours. I then put it in full choke and pulled twice. Put it it fast idle and pulled 3-4 times. Put it in main position. Nothing. No fire, no hint of combustion.

I also noticed it appeared that fuel was leaking out from the muffler/exhaust, after that attempt. The leak was profuse. 

The saw is about 5 years old, no older than 6. It is a standard start model- it is NOT an EZ Start. It did not see much use until I got it, and then it has seen light duty use for small kindling cutting, branch trimming, etc. 

I have resurrected 40 year old Blue Homelite's that have been trashed with less problems than this saw has given me. 

Again, the following has been confirmed:
-coil cleaned and gap checked, cleaned all ground and wire connections
-new NGK plug, plug interchanges with Bosch WSR6F
-Verified that spark exists
-I know the engine is getting fuel, when pulling the plug after cranking, it is often a little wet. 
-replaced the old carb with a known good carb.
-carb is the Zama unit with a limiter cap
-new air filter
-new line from tank vent to vent
-new fuel line and new strainer
-Non-ethanol 89 octane gasoline, 2cycle oil, mixed according to manual for 1 gallon
-Yes, I'm pulling hard enough. I have several of huge, high compression Homelites with no compression releases that can be very cold collared and my 250lb frame hasn't had problems cranking those
-I am using the standard procedure for 2 stroke starting

Any thoughts on where to go from here, other than the standard Internet responses like "Send it me, a-yhull-yhull-yhull" and "Burn it to the ground" ?

I really appreciate your responses(even "send it to me" and "Burn that M*******ker down") and I thank you for reading.


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## wkeev (Nov 23, 2012)

It sounds like its flooded . Take out the plug and turn upside down and pull over . Then blow air in the plug hole as you pull it over . You may need to let it set for a while and install a new plug . I had a freind that did the same thing to his MS 250 last week.


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## indiansprings (Nov 23, 2012)

Time for a carb rebuild. Reset your H&L back to to factory settings. May sure your inlet screen is clean if you don't have access to a ultra-sonic cleaner.


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## greg409 (Nov 23, 2012)

I noticed you "disassembled & reassemled" the carb last year - it then ran fine.

Did you rebuild it with new diaphrams?

It ran for a few seconds, was it simply burning out the crankcase fuel (flooding)

Then it's running out of the muff (not uncommon with a stiff diaphram or "gummy carb")

You may find it'll start in the next day or so, as the new fuel loosens everything up, but I'd imagine it could use a going-thru'

please post back

luck,greg


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## fearofpavement (Nov 23, 2012)

If you haven't yet, take off your muffler and check your piston to make sure it isn't scored. Simple to do and good thing to check off the list.


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## lambs (Nov 23, 2012)

Are you getting a blue spark?


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## biggus (Nov 23, 2012)

Have you checked to make sure the metering level is set right? Most carbs need the metering lever set flush w/ the carb body. You can hold a straight edege over the carb body and make sure it's flush. If it needs adjustment just bend the tab in the proper direction.


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## d1hamby (Nov 23, 2012)

*old fuel?*

I always ask the stupid questions first? Is the fuel fresh?


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## bigv (Nov 23, 2012)

I want to thank all of you again. 

Here is what I've done currently, and I will reply back after morning with more info: 

The spark looked more white to me, but with all of the plastic around the engine, it was difficult to see. It may indeed have been blue, but all I saw was a white light. 

The fuel is indeed fresh, it is non-ethanol 89 octane. The 2 cycle oil is Husquavarna's brand, I bought a huge case of the little bottles at an auction for the price of a 12 pack of Walmart cheapos- and as best as I can tell, the Husky oil is good oil. 

The pld carb was flowing well enough to flood it, the new carb I have installed was on a known good, working 025 that an Ebay seller was parting out. I believe him when he says it was working. 

I removed the muffler, cleaned it, and cleaned the spark arrestor. I saw no signs of scoring. 

It was massively flooded, much worse than what I had thought, and much worse than what I though it would be. Knew it was flooded, but I didn't think it was flooded as bad as it was. 

I will get a kit for the old carb and try to go through it again, as insurance.


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## H 2 H (Nov 23, 2012)

95 % of the time it's the carb problem

I doesn't take much time at all to rebuild a carb

Just make sure when your not going to use your saw for 3 weeks dump the gas in saw into your truck and start your saw up and run it dry


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## s219 (Nov 23, 2012)

Am I reading right that you left old fuel in the saw from April to October? That's asking for trouble, so I'd go over the entire fuel system, especially if that was ethanol fuel.


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## bigv (Nov 24, 2012)

SUCCESS ON THE MS250 ! SUCCESS ON ANOTHER FRONT !

I had fresh fuel in it, no scoring, spark appeared white rather than blue.

I had let the muffler dry out over night, and also the cylinder.

I put everything back together, and after 2 pulls on full choke, it popped. I switched to fast idle, one pull- it roared this time and cut off. Then run position, it started on the first pull and idled beautifully. 

Waited 2 hours, as it had dropped 10 degrees over that time, and even with the saw really cold, it started first pull again. 

Now the other front....

The funny thing is, I had gone to a local flea market this morning to look at a Farm Boss Husquavarna- I did not think I'd get the MS250 to run. The guy who had it, also had an 025, and while he was asking more than new on the Husquavarna, he wanted $40 for the Stihl 025. I figured I would buy it for parts. He said he could not get it to run, probably scored, basically called it a trash saw. 

After I got my MS250 running, I took the carb I had rebuilt for the MS250(it was the original carb I replaced yesterday), put it on the 025. I always check any saw I buy to make sure there is no scoring and that it isn't so dry it will dry score or lean score. I made sure the cylinder was primed a little because it was super dry, and I pulled it over a few times with the muffler and the plug out. In that process I realized that the saw had not been run much at all. I replaced the plug with a new NGK, followed the service manual procedures for setting the carb, and put everything back together. I cleaned the coil area, and the coil pickup was a little crusty, but it appeared the saw was new inside, and scotch brite cleaned up the pickup. I scotch brited the flywheel surfaces, and then put that back together. 

Two pulls on full chocke and it popped, although not too enthusiastically. One pull on fast idle and it revved to life, and died after one press on the throttle. One pull on run position and it ran, a little too fast idle, I adjusted the idle and the carb one more time because it still felt a little rich. Now it starts first pull when warm. 

That occupied the two hours in between working on the MS250. 

I love buying things other people have given up on and being able to take time and care to fix them. 

I now love these saw. They're nice, consumer grade saws, which is exactly what they are supposed to be.


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## Dan_IN_MN (Nov 24, 2012)

Good to hear you got the little guy running!

One thing about 2 strokes is that they will not run with liquid fuel in the crankcase. Sounds like yours was loaded with fuel.

I too like taking other peoples 'junk' and getting it running!

REP sent!

Oh, when you're ready for that little saw to have a bit more power, open up the muffler a bit. search muff mod (be sure to retune by opening the H screw on the carb bit when you do this)


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## PRS (Dec 5, 2014)

bigv said:


> Howdy, Gentlemen:
> 
> Two years ago I purchased a Stihl MS250, used. It ran well the first year. Next year I had issues with it not wanting to start. I determined I was getting spark, so I disassembled the carburetor completely, and then used carb cleaner to clean out all the small passages in the carb. I used the Carb Cleaner's plastic straw to run pressurized cleaner through each and every passage.
> 
> ...


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## PRS (Dec 5, 2014)

This may be to late to help bigv, but... I had a hard to start ms250. I tried everything related to fuel/carburetion... rebuild carb, new fuel filter, new fuel line, new impulse line, fresh fuel with Stihl oil, even a new spark plug. Still hard to impossible to start. I found the ignition module to be working intermittently. I installed a new one. End of problem. With reliable spark the ms250 now always starts easily and runs well. I don't know if other Stihls have this problem, but if your ms250 won't start and you've tried fixing all the fuel related items..... try changing the ignition module.


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## Timothy Smith (Jun 15, 2018)

I also had a non-starting MS-250. I had used it just days earlier and stopped it with fuel in the tank. A few days later it wouldn't fire, absolutely nothing. I spent at least 6 hours troubleshooting and couldn't find any cracked lines, clogged filters, and anything obvious. The saw is only 2 years old and I probably cut only about 5 cords of wood during that time. 

I finally gave up and bought a carburetor kit on ebay for $15 including shipping. I replaced the carburetor, air filter, fuel filter, fuel line, and impulse line. It turned over on the third pull on the choke setting and fired on the next pull on the half choke setting. The best part is that the saw runs noticeably stronger than it did originally. My suspicion is that the Chinese built replacement carb was designed and tuned for optimal performance without concern for emissions.

Two points on the new carburetor: 1.) the high and low adjustment screws are located about 1/16 of an inch apart while the original was about 1/2 an inch apart. Both screws on the new carb should be accessible through the high adjustment access hole. If not, you'll have to remove the cover to make adjustments. 2.) also the spring on the choke shaft that controls the choke valve (stihl calls it a "choke shutter") was too loose to open that valve when you squeeze the throttle so I had to tighten the spring by one turn. 

Hope this helps someone who is cussing at your MS-250. Spend the $15 bucks (or $19 and get the ignition module too) and don't waste 6 hours like I did. Good luck.


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## prm510 (Jun 15, 2018)

PRS said:


> This may be to late to help bigv, but... I had a hard to start ms250. I tried everything related to fuel/carburetion... rebuild carb, new fuel filter, new fuel line, new impulse line, fresh fuel with Stihl oil, even a new spark plug. Still hard to impossible to start. I found the ignition module to be working intermittently. I installed a new one. End of problem. With reliable spark the ms250 now always starts easily and runs well. I don't know if other Stihls have this problem, but if your ms250 won't start and you've tried fixing all the fuel related items..... try changing the ignition module.



You’re not alone on that one. When I bought my MS250 last year it started without issue then it started giving my grief. I, like you, checked plugs, carb, rebuilt carb, etc. until I replaced the ignition module. That thing fires right up no problems on 1/2 after two pulls. I love the saw- but finding the issue was a pain for sure.


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