Stihl MS250 dies when I give it gas.

[HankG]

I have a MS250 that's only two years old and has barely been used. I doubt it has more than four or five hours on it. It will start up with some work, but it idles for a couple seconds then dies most of the time, and when it doesn't die on its own, it dies when I try to give it any gas. I asked my brother to take a look at it since he's fixed a number of chainsaws, and he says it looks like it isn't getting fuel. We pulled out the carb and opened it up, and the check valve looked perfect and everything was as clean and shiny as you'd expect a basically brand new saw to look. It did sit with gas in it for a while, but there are no visible signs of any damage to the carb as a result. I tried putting new gas in it and starting it up but it didn't make a difference.

Does anyone have any ideas about what could be wrong and how to fix it?

Thanks for any help.

 

[lone wolf]

I have a MS250 that's only two years old and has barely been used. I doubt it has more than four or five hours on it. It will start up with some work, but it idles for a couple seconds then dies most of the time, and when it doesn't die on its own, it dies when I try to give it any gas. I asked my brother to take a look at it since he's fixed a number of chainsaws, and he says it looks like it isn't getting fuel. We pulled out the carb and opened it up, and the check valve looked perfect and everything was as clean and shiny as you'd expect a basically brand new saw to look. It did sit with gas in it for a while, but there are no visible signs of any damage to the carb as a result. I tried putting new gas in it and starting it up but it didn't make a difference.

Does anyone have any ideas about what could be wrong and how to fix it?

Thanks for any help.

First turn the jets out counterclockwise about about 1/8 turn if that dont help try a new gas filter.Then I would check the fuel line for a leak then try a new rebuld kit in the carb.

 

[REJ2]

I have a MS250 that's only two years old and has barely been used. I doubt it has more than four or five hours on it. It will start up with some work, but it idles for a couple seconds then dies most of the time, and when it doesn't die on its own, it dies when I try to give it any gas. I asked my brother to take a look at it since he's fixed a number of chainsaws, and he says it looks like it isn't getting fuel. We pulled out the carb and opened it up, and the check valve looked perfect and everything was as clean and shiny as you'd expect a basically brand new saw to look. It did sit with gas in it for a while, but there are no visible signs of any damage to the carb as a result. I tried putting new gas in it and starting it up but it didn't make a difference.

Does anyone have any ideas about what could be wrong and how to fix it?

Thanks for any help.

Welcome everyone the newest member to the Husky camp!! congrats on seeing the light:hmm3grin2orange:

 

[dswensen]

Something may be amiss in the low or high speed circuit of the carb. With the carb apart, make sure all the passages are clear. Use low pressure compressed air, and a stiff paint brush bristle to check them all. Sounds like a blocked passage somewhere to me. Or maybe gas varnish in the screen filter at the base of the metering needle.

 

[lone wolf]

Something may be amiss in the low or high speed circuit of the carb. With the carb apart, make sure all the passages are clear. Use low pressure compressed air, and a stiff paint brush bristle to check them all. Sounds like a blocked passage somewhere to me. Or maybe gas varnish in the screen filter at the base of the metering needle.

I read on here the other day some carbs can be damaged with compressed air.That would explain why sometimes they cant be fixed maybe the air is ruining something like a check valve I will wait for the masters to chime in on that.

 

[albert]

Check the fuel hose, famous for cracking.

 

[Warped5]

I read on here the other day some carbs can be damaged with compressed air.That would explain why sometimes they cant be fixed maybe the air is ruining something like a check valve I will wait for the masters to chime in on that.

Correct ... some carbs can be damaged by compressed air.

I prefer a soak in Sea Foam while in a USC for :30.

 

[HankG]

Thanks for the replies; I'll try out these suggestions.

 

[lone wolf]

Correct ... some carbs can be damaged by compressed air.

I prefer a soak in Sea Foam while in a USC for :30.

No wonder I dont have any luck with the damn things!Sea foam and an ultrasonic and thats it huh what is your success rate?Do you need to pull those small pie shaped plugs?

 

[Captain Crunch]

I take off everything can come off. If the kit comes with welch plugs I take those out too.
I use a USC also, but just near boiling hot water with a few drops of simple green or such. 6 to 10 minutes. Very good success rate. Of course if your fuel line is cracked, all the carb cleaning in the world won't fix it.

I would also like to know more about compressed air damaging a carb. Damaging what, on what carbs? Inquiring minds want to know.

 

[Warped5]

No wonder I dont have any luck with the damn things!Sea foam and an ultrasonic and thats it huh what is your success rate?Do you need to pull those small pie shaped plugs?

Success rate is pretty good, ran into a difficult carb once and used a slingshot to launch it over the house across the street: Problem solved! Never pull the plugs unless I think I have to .... very rarely.

 

[Warped5]

I take off everything can come off. If the kit comes with welch plugs I take those out too.
I use a USC also, but just near boiling hot water with a few drops of simple green or such. 6 to 10 minutes. Very good success rate. Of course if your fuel line is cracked, all the carb cleaning in the world won't fix it.

I would also like to know more about compressed air damaging a carb. Damaging what, on what carbs? Inquiring minds want to know.

When I was still pretty green on this stuff, some respected members here told me to stay away from the compressed air. It could potentially damage internal check valves. I have not had enough failures to doubt them, that's all.

 

[lone wolf]

That explains why they run worse after i rebuild them!:bang:

 

[angelo c]

I guess that all depends on your oppinion of what "compressed air" is or isn't...

kinda like Bill Clinton when he says(....o never mind...)

6-10psi probably no problem

80-100 psi....mmmm... problems.

 

[Captain Crunch]

Internal check valves? Where are these located and on what carbs?
After I strip down my walboro wt, I see nothing but tiny drilled passages and a needle seat. Not trying be a smart Alec here, would like to learn and be "smarter".

 

[w8ye]

The one that is often damaged by compressed air is the one inside the high speed nozzle.

The high speed nozzle protrudes into the venturi. In the metering chamber, you sometimes see its backside. Don't blow down through the high speed nozzle as the check valve cage is delicate.

On the single needle Walbro in a 025 there are two other little brass plugs with holes through them in the floor of the metering chamber. The one that is screwed in is the high speed jet. The one that is pressed in is the intermediate jet.

 

[dswensen]

I read on here the other day some carbs can be damaged with compressed air.That would explain why sometimes they cant be fixed maybe the air is ruining something like a check valve I will wait for the masters to chime in on that.

which is why I recommended low pressure compressed air.....

 

[Deets066]

I just worked on my grandpa's ms 192t. It would do the same thing, die when you give it fuel, It would also idle way down when I was adjusting the carb, not from turning the screws all you had to do was just push on it a little and it would almost die. After a little looking, the two nuts that hold the back of the carb and filter housing were loose, I tightened them up and it ran like a top.