Stihl MS250 mixture screws?

[dodge man]

I have a Stihl MS250 that is about 15 years old. I would call it occasional usage but over the years it has accumulated some hours. Newer spark plug and air filter.

Problem has been going on for a couple years. It will idle badly but keep running if you goose the throttle a little. It will also bog down and die unless you work the throttle slowly when going to full throttle in wood, but once pulling hard it runs fine. Last time I used it I played with the two screws a little to make it idle better and transition to full throttle better. It ran perfect. Problem is the will most likely repeat where it will run bad.

I do not think it is fuel. I have several Stihl tools and all run the same fuel and they run fine.

 

[pmsmechanic]

I've had reasonable luck just gently turning in the screws till they seat and then turn them out again to where they were. What this does is clean junk out of the seat. It also helps to gently turn the screws in till they seat counting the turns on the way in. Then remove the screws and flush the hole out with a bit of brake clean.

If that doesn't work then you will eventually need to take the carburetor apart and clean it.

 

[pmsmechanic]

Double post grrrr!

 

[dodge man]

Thanks. I wondered if the carb needed cleaned.

 

[ovrszd]

I've got a 9 yr old 250 and a 361.

The 250 is very picky in regards to fuel. You have to feather the throttle to get it to rev up. The 361 never acts that way.

May be a simple adjustment but I've always gotten over it with fresh fuel.

I'm curious to see if you find an adjustment solution that might make mine not so picky.

 

[ericm979]

It sounds like it's a bit lean. A little richer on the low speed should help that.

When I end up with carb settings that keep going off, I return the settings to the default (usually 1 turn on Stihls but check the manual) and tune from there. Sometimes you can get a setting that seems good but is way off the factory setting and won't be good the next time you run the saw. Starting over often fixes it.

 

[ruffdog]

If simple adjustments/repairs don't get it running right, you may have a air leak. That may be a bad crank seal, pulse line, or the clam shell joint leaking air.

 

[dodge man]

I have backed the mixture screws in and out to the factory settings. The turns is printed on the side of the saw. It could be sensitive to fuel. This last time it ran good it had newer fuel. I guess just because my other stuff runs fine doesn’t mean the saw is not mo sensitive.

 

[ericm979]

Some of my two stroke equipment is fairly insensitive to fuel age. I have a Husky backpack blower which runs terribly unless the fuel is fresh. It's carb is totally non adjustable, not even tamper resistant adjusters (which I have the tools for). A slightly richer mixture would fix it but there's no way to change it.

 

[pmsmechanic]

Some of my two stroke equipment is fairly insensitive to fuel age. I have a Husky backpack blower which runs terribly unless the fuel is fresh. It's carb is totally non adjustable, not even tamper resistant adjusters (which I have the tools for). A slightly richer mixture would fix it but there's no way to change it.

So look for an older Husky with the same model engine and buy an adjustable carb for the older model. They run about $40 on the internet.