Saw won’t stop

[Tjstampa]

I bought a new ms250 for my Christmas gift. Just got a chance to start it today. The choke control felt a little spongy but I eventually got it started. Just as I was going t work on branch my son comes running towards me. I go to shut off the saw and it won’t turn off. Finally pulled the cover and took the plug wire off. It is under warranty and is already packed up to go back to the dealer. I am just wondering what would cause this.

 

[Chainsaw Jim]

If came from the factory that way then it's anyone's guess.
Did you pull the throttle trigger in while engaging the choke? If not then you may have tweaked something.

 

[heimannm]

Sthil saw have a master control switch with both the choke and stop switch functions combined into one lever. When you move it to full stop, there is supposed to be a contact on the lever that grounds out the primary circuit of the ignition. Could be the wire came loose, or the contact fell off, or the mechanism has been tweaked and the contact is not actually grounding as it should.

Mark

 

[Wood Doctor]

Sthil saws have a master control switch with both the choke and stop switch functions combined into one lever. When you move it to full stop, there is supposed to be a contact on the lever that grounds out the primary circuit of the ignition. Could be the wire came loose, or the contact fell off, or the mechanism has been tweaked and the contact is not actually grounding as it should.

Mark

Mark is correct. If this ever happens again, move the lever to choke position and that should kill the engine. I believe the MS250 has no decomp valve, but for saws that do, pressing in the decomp valve and holding it down will usually kill it also.

 

[MustangMike]

Everything I was going to say has been said!

Also, I've seen wood chips get into the control lever and insulate it from grounding.

 

[kfd518]

Everything I was going to saw has been said!

Also, I've seen wood chips get into the control lever and insulate it from grounding.

Or on an unrelated husky 288 stick the throttle open at 3/4 throttle! That surprised me! Hah hah

 

[dougand3]

Here is an MS250 in Stop / Off position. See the contact band touching the wire female connector. As said above - if you ram it to choke w/o a trigger blip, it can torque plastic.

 

[Tjstampa]

I tried to short out that connection with a screw driver but nothing happened. I haven’t even been able to get it in wood yet. Did not think of choking it off. I am thinking the ground wire is nit connected but Since it under warranty will se what the dealer says

 

[Wood Doctor]

Not quite the same issue, but recently I rebuilt an MS661C that was crushed by a big log. The tank housing handle was broken completely off. The saw kept running at WOT. Since the switch rod was useless and the saw was pinned under the log, the crew had to wait until it ran out of fuel. The sawyer had removed the fuel cap, but could not pour all the fuel out of the tank.

After $400 in parts and ten hours of labor, it's back in business. Needless to say, I said a short prayer before I tried to start it after the rebuild. It was a small miracle that it fired up and ran as if nothing had happoened.