Stihl MS 250 shutting down

[NuclearNick]

Hello all,

I've been using an MS 250 for about 10 years for limbing, etc and it's been very reliable. Went out to use it today (haven't run it in about 2 months) and it starts just fine but dies off after I run it for a few minutes, usually when I get done with a cut and let off the throttle. Hard to start after it dies - have to put it in full choke and give it a pull, then starts after a few pulls in half choke. Drained gas that was a few months old, put in new gas. Replaced air filter with new air filter, same problem. I haven't attempted any surgery yet. Willing to pull this thing apart, but don't want to do so randomly.

Any sharp Stihl mechanics out there with ideas what might be causing this? It's been a good little saw and I'd like to keep it running a few more years.

Thanks!

 

[TRTermite]

Hello all,

I've been using an MS 250 for about 10 years for limbing, etc and it's been very reliable. Went out to use it today (haven't run it in about 2 months) and it starts just fine but dies off after I run it for a few minutes, usually when I get done with a cut and let off the throttle. Hard to start after it dies - have to put it in full choke and give it a pull, then starts after a few pulls in half choke. Drained gas that was a few months old, put in new gas. Replaced air filter with new air filter, same problem. I haven't attempted any surgery yet. Willing to pull this thing apart, but don't want to do so randomly.

Any sharp Stihl mechanics out there with ideas what might be causing this? It's been a good little saw and I'd like to keep it running a few more years.

Thanks!

I may sound way off target but one of my 025 saws has done this to me twice. The original coil then a used oem coil , Has a chinese critter in it now and has been 4/5 years but it doesn't get the workout it used to get..

 

[ballisticdoughnut]

Have you made any adjustments to the carb?

 

[NuclearNick]

Have you made any adjustments to the carb?

Not yet. Wondered if it may need a carb cleaning. Not sure if this little carb can be pulled apart and cleaned or not, or if it's just a throw away.

 

[PithFreak]

Make sure the spark arrester screen isn’t clogged, take that out and torch it to burn it clean

 

[TRTermite]

Not yet. Wondered if it may need a carb cleaning. Not sure if this little carb can be pulled apart and cleaned or not, or if it's just a throw away.

They are easy enough to work on (My Opinion). Most times the single (Low mix only) carbs get swapped out with a High/Low carb.

 

[NuclearNick]

Make sure the spark arrester screen isn’t clogged, take that out and torch it to burn it clean

Looking for a spark arrestor on this thing, not seeing it. Any idea where it's at?

 

[sundance]

Looking for a spark arrestor on this thing, not seeing it. Any idea where it's at?

should be on the muffler outlet.

 

[PithFreak]

Looking for a spark arrestor on this thing, not seeing it. Any idea where it's at?

Should just be behind the exhaust, unfasten the 2 8mm nuts on the studs and take the vent plate off

 

[NuclearNick]

Should just be behind the exhaust, unfasten the 2 8mm nuts on the studs and take the vent plate off

Perfect, that worked. Spark arrestor was clean, I don’t think that’s my problem. Next step is to adjust carb settings I suppose.

 

[ericm979]

Take the muffler off and inspect the piston through the exhaust port. If it's damaged like from a partial seizure, it's almost always on the exhaust side. Take some pics and post them.

 

[NuclearNick]

Take the muffler off and inspect the piston through the exhaust port. If it's damaged like from a partial seizure, it's almost always on the exhaust side. Take some pics and post them.

Great idea. Turned it slowly and took a few pics, looks clean and smooth to me. Also pulled out the plug, gap at 0.020”, doesn’t look too fouled.

 

[Jasonrkba]

Get that carbon out of the exhaust port before it scores that minty piston. Your probably having carb issues. Get a good rebuild kit and replace the plug. Also if the fuel and impulse lines are original they are ready.

 

[user 74409]

Cracks in the fuel line are common with MS250 when saw is 10 years old. Cracked fuel line will give same symptoms you are experiencing with your saw. Fuel line is molded and I usually choose OEM Stihl part after a couple of poor experiences with aftermarket versions kinking and not working right. Fuel line can be changed without removing orange handle but requires removing air filter and carburetor and plenty of patience.

 

[NuclearNick]

Get that carbon out of the exhaust port before it scores that minty piston. Your probably having carb issues. Get a good rebuild kit and replace the plug. Also if the fuel and impulse lines are original they are ready.

Any suggestions on where to get a good carb rebuild kit? Amazon, or does Stihl sell kits?

 

[Jasonrkba]

Ebay

 

[ericm979]

That's a lot of carbon. What oil are you using?

Have you changed the fuel filter ever? Might be worth doing so.

No need to rebuild the carb unless you know it's the problem. Saw carbs have some small delicate parts in them.

The OEM carb is a known quality piece. AM carbs can be anywhere from ok to junk. Same with carb parts.

 

[user 74409]

Zama RB-105 for full kit and GND-35 for just diaphragms & gaskets. eBay is good source.

 

[Jasonrkba]

That modle had about four options of carburetors. Both zama and wabro.

 

[TRTermite]

Thread / MS440 Running Problem Read Post #6 by Old Stroke Or go up to post #2 on this thread. I am going back to the peanut Gallery.