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MS 250 hard to start when hot

Discussion in 'Chainsaw' started by vonb, Jul 14, 2019 at 6:43 AM.

  1. vonb

    vonb ArboristSite Lurker

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    I have a MS 250 that starts fine when cold provided I follow the 3 pull rule on full choke. However, when running after 30 minutes or so, it starts to die in the middle of a cut.

    Also, it is a bear to get re-started after a fill up when hot. I thought it might be vapor locking. However, that doesn't account for the hard starts after removing cap and filling up. Any ideas?
     
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  2. Cliff R

    Cliff R Addicted to ArboristSite

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    Does it do this year round in any weather or only when it's hot/humid outside?.......Cliff
     
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  3. andrewsc

    andrewsc ArboristSite Lurker

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    Ignition coil could be going bad.

    Sent from my SM-S767VL using Tapatalk
     
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  4. vonb

    vonb ArboristSite Lurker

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    I haven't noticed it before this weekend. I was cutting a couple days ago for three hours and it was definitely hot and humid in Tennessee.
     
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  5. Cliff R

    Cliff R Addicted to ArboristSite

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    If it only does it in really hot weather then it's a heat related issue.

    I have a few saws that are difficult to re-start after re-fueling, but they only do it when it's really too hot out to be cutting anyhow. This new fuel has a low boiling point, plus ethanol and oxygenated, etc. I've noticed it fairs poorly in some saws when it's over 90 degrees outside and very humid.......Cliff
     
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  6. HarleyT

    HarleyT Tree Freak

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    For starters, pull off the muffler and look at your piston. Also, remove the air filter cover and look for cracks in the fuel line, flex it with your finger, to check for the cracks.
     
  7. lone wolf

    lone wolf MS 200T King

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    Its either vapor locking from winter fuel or a bad coil.
     
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  8. vonb

    vonb ArboristSite Lurker

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    I was using what was purported to be non-ethanol fuel (93 octane). The saw was given to me by Dad as he was fed up with it. I thought it to be user error as I had never had issues with it prior to him using it. I've now experienced his similar issues. Nothing more frustrating than to be in a felling cut and have a saw die from max throttle.
     
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  9. lone wolf

    lone wolf MS 200T King

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    Look at the spark when cold on the plug then run the saw till it happens and see if the spark is weaker ,it sure sounds like a coil is bad.
     
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  10. HarleyT

    HarleyT Tree Freak

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    Even more reason to do look at the piston and check the fuel line.
     
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  11. Cliff R

    Cliff R Addicted to ArboristSite

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    Vaporizing fuel isn't limited to Ethanol type fuels, non of this new fuel has the specific gravity or BTU content pound for pound as older fuel formulas did.

    Even so I've not had issues when running with any of it, but had it rear it's ugly head after hot shut-down, but only on the hottest summer days. This is why I never take less than 3 saws on any outing, and quit re-fueling them or touching up chains in the field. I just grab another saw and keep cutting.

    I'll also add here that just a month ago I got some "bad" gas. Everything I put it in started to run like crap, starting with my Echo string trimmer that's been flawless since around 2003. I had to re-adjust the L and H screws and thought it was in need of a carb kit. Then one by one the saws I just fueled started acting up in similar fashion and the "light bulb" goes off, common denominator the new fuel I just put in them.

    I dumped it out, and funny thing is that it would BARELY burn when you threw a match to it, more like kerosene than gasoline.

    Went to a different station and re-filled with 93 octane E-10, and power is restored.......Cliff
     
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  12. drf255

    drf255 BAD CAD

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    Step 1 , change the $2 spark plug.

    Also check the piston as said above.

    I spent $200 and countless hours on a 4 stroke HondaGX engine. New coil, carb, fuel tanks. Adjusted valve lash, etc... guess what it was in the end?

    May not be issue, but it’s a cheap test.
     
  13. pioneerguy600

    pioneerguy600 Lost in Space Staff Member

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    Leaning more toward a module issue as it takes more than 10 mins of run time before it starts acting up. Sparkplugs tend to act up very soon after start up, they heat up faster and a crack in the ceramic or carbon fouled will short out very quickly.
     
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