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stihl ms 250 help

Post in 'The Gear' started by bull, Jan 6, 2012.

  1. bull

    bull Member

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    i have a stihl ms 250 chainsaw that will start and run fine for a min or two and shuts off and wont start . anyone having this trouble

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  2. LLigetfa

    LLigetfa Minister of Fire

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    Loosen the gas cap and try again.
  3. Freeheat

    Freeheat Minister of Fire

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    Usally Its a fuel line problem. How old is it?
  4. JoeyD

    JoeyD Minister of Fire

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    I vote gas cap.
  5. bull

    bull Member

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    guy gave it too me said he thought the rings and piston was burned up. or got too hot ?????
  6. amateur cutter

    amateur cutter Minister of Fire

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    Compression test it? Check on the exhaust side for scoring on the piston. A C
  7. n6crv

    n6crv Feeling the Heat

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    Check the pulse tube. Noted to get hot then crack.
  8. MasterMech

    MasterMech Guest

    Do the easy stuff first. Once it stops, check it for spark. Does it restart once it cools? Then move to the fuel/impulse lines. Then look for compression/piston & cyl issues.

    Most fuel line issues are there hot or cold, some only present with the tank less than completely full. Gas cap on these saws isn't vented so it's seldom the problem. There is a tank vent attached via a line to a check valve near the air filter. Pull the line and re-test the saw.
  9. LLigetfa

    LLigetfa Minister of Fire

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    I don't think anyone suggested the cap was the problem but loosening the cap is the quickest way to check for plugged vent. Much easier than pulling the line.
  10. MasterMech

    MasterMech Guest

    Joey D said try the cap and with the MS250, it's a flippy cap. Loosening the cap and re-running the saw to test is a good way to get pants that smell like premix.
    n6crv likes this.
  11. LLigetfa

    LLigetfa Minister of Fire

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    He doesn't need to buck up a cord of wood with the cap loose, just see if it recovers while stalling or to hear the telltale sound of releasing a vacuum.
  12. laynes69

    laynes69 Minister of Fire

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    With our 025 the slightest pull on the saw and the impulse tube can disconnect. I just fixed mine, which was a crack at the tank in the gas line. Took less than 10 minutes to fix. I vote a bad lined either at the impulse or fuel. Good little saws.
  13. Den69RS96

    Den69RS96 Member

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    My guess is either a plugged vent or a bad coil
  14. Danno77

    Danno77 Minister of Fire

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    +1. I'd lean more towards the coil, though.
  15. Grannyknot

    Grannyknot New Member

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    Has anyone ever changed the in-tank fuel pickup filter in one of these?
    I have an old 024 that I'm thinking could use this, but not sure how to access it for service.
  16. Danno77

    Danno77 Minister of Fire

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    Most are pretty easy, take a piece of wire, make a small hook at the end, fish the line out, but don't pull on the hose too hard. Then pull the filter straight off and put the new one on, then stuff the filter back in...
  17. Grannyknot

    Grannyknot New Member

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    so you've done it without taking the tank apart?
  18. Danno77

    Danno77 Minister of Fire

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    That's what it shows in the 250 manual, but it's for 210, 230, and 250's, so I can't promise an 024 is the same. My 170 is easy like that, too. It's been a few years on the 028, but pretty sure that's how it goes, too. I'll check that manual as well.

    Should be able to do it out in the bush if you need to!

    Edit: yep, 028 is the same way.
  19. MasterMech

    MasterMech Guest

    That's pretty much how it goes on all handheld equipment these days.
  20. StihlHead

    StihlHead Guest

    I have owned maybe a dozen of the Stihl 021/023/025/210/230/250 saws. The typical reason that these saws fail like the OP here is a crack in the impulse line. That runs from a nipple at the base of the engine block to a stub behind the carb input. It drives the tiny fuel pump in the carburator. Any air leak in the impulse line and the carb will starve for gas, as if there is a crack in the gas line (which is also a common failure in any Stihl saws after a couple of years) or a clogged fuel filter. This problem can also be due to more subtle things, like a clogged muffler screen, or a clogged air filter. It is rare that the coils fail; when they go they go and they do not start at all. Spark plugs fail over time, but the saw starting and then not running is more typical of a gas or impulse line problem, or a clogged air filer or muffler screen. It can also be a really badly tuned carb (L screw set way off or idle set too low).

    Pull the muffler cover plate and check that the spark screen is not clogged up (I have had that happen, especially when I was using Castrol FB premix oil). If it is clogged up twist the screen to unclog it. I recommend running a 100% synthetic premix oil (rated JASO FC or FD) to avoid clogging the muffler screens and they run better on that stuff. Clean the air filter after use. As others have said here, fish the gas filter out of the tank with a metal wire hook (old coathanger wire workd good for this). If it is clogged up replace it. They are cheap. Typically they are not clogged enough to stop a saw though, unless you have dust in the tank or it is really old. Look for small hairline cracks in the gas line. Typically when gas lines crack Stihl saws do not start at all though. Also replaceable for fairly cheap, and if you replace a gas line replace the filter at the same time. If it is the impusle line... they can be a PITA to replace. You can get to them behind the coil/flywheel with needlenose pliars if you know where it is and where they connect to. Nimble fingers help here. I have done it a few times of several Stihl saws, and have loaded the air with lots of choice words doing them. They can come loose as well and be nudged back in place with your tank filter puller/coathanger wire tool.

    BTW: I picked up a Stigl MS 211 for a friend in New Zealand recently and they are nice little saws. More power than a 210 and lighter, and far less vibration. With a picco bar and chain they are a geally nice limbing saw. Actually I dropped an 18 inch DBH birch tree here with it and cut it into firewood in an afternoon. I plan on replacing my 025 with it soon (I have the 026s which I use far more than the 025 anyway).
  21. Grannyknot

    Grannyknot New Member

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    Great information, thanks for taking the time to type this.
    I'm having similar problems that the OP is having, except mine runs decent for about 10 minutes (smokes a little), starts to get weak, and then shuts down and won't start until the next day.
    I'll probably try checking a few of the above mentioned fixes.
  22. Den69RS96

    Den69RS96 Member

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    I agree with Stihlhead except for the part about coils. A bad coil doesn't necessarily mean the saw will not start. A bad coil will become apparant once the saw is warmed up and then it will just quit running and won't start again until the saw has cooled down. In this situation, 9 out of 10 times the coil was the problem.
  23. StihlHead

    StihlHead Guest

    I have had those symptoms in a 210 and a 250/025 hybrid that I Frankenstiened, as well as an older 026 that I still have. They ran fine until they got really hot after an hour or so of use and then they did not want to start. I typically swap the ignition modules (the coils) in problem running saws with another one to test them. In my experience, the case of a Stihl not running as soon as it is warm is more typical of the impusle line failing, or the carb needs tuning (or there is a probelm in the air or gas flow). Coils take more time to heat up and the electronic ignition can fail in them. Coils on Stihl saws are really spendy though, and the last thing to replace in my book. If all else fails, then I look at the ignition. I usually will test a failing saw with a spare plug to see if there is a spark and then leave it to tear into later in my shop. I always take 2 saws into the woods for cutting with, and I always have a spare loop for each bar that I have. I run 3/8 0.050 bars on all my Stihl excet the 025 for simplicity sake.

    If you have more than one chainsaw, I would invest in a good digital tach and tune them yourself. They run about $90 but a good tach can save you from a too-lean running saw and burning up a cylinder. I use a TECH-TACH TT-20K, a wireless hand held tach.
  24. LLigetfa

    LLigetfa Minister of Fire

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    The OP mentioned one minute or two, not hours. Hard to imagine a coil could heat up in that short a time.

  25. StihlHead

    StihlHead Guest

    Yah, in my experience, "the saw runs for a minute or two and dies" are typically impusle line problems, as the gas in the carb is sucked dry and the impulse line does not feed it. That was my point, or I thought...

    The longer run time failures can be several things, such as the heat vapor locking the carbs, ignition modules overheating, etc. The 025/250s have a heat shield between the muffler and the engine that the 210 does not have. They (the 025/250s) get hot. The 1123 line of saws also have the summer/winter flippey thingey between the spark plug and the air filter. You want them in the right position. I tend to leave them in summer mode, as I do not cut much when it is below freezing. Supposedly it helps keep the carb from icing up in winter but I leave my saws in the garage and they are never at outdoor temperatures when I run them in winter. The summer/winter flippy thingey is a loose piece in that line of saws too, so they tend to get lost over time.

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