Stihl ms 250 problems please help

[Charlieh]

could be the fuel tank breather needs cleaning, sounds like it could be restricting flow of fuel when the saw starts which would cause it to act as described.

 

After it you have tried starting it a couple of times open the filler cap slowly and see if it sucks air inwards (although this probably isnt so easy on those horrid flappy type fillers)

[gazzapowells]

hi

 

saw is started on full choke then move it to 1/2 choke... when it starts revs up about normal for 1/2 choke but when you blip throttle it cuts out...

if dont touch throttle runs for about 10 secs at most!

 

and yes the ms has the filter wish just clips on...

 

 

thanks

 

 

 

How high is "high" - I mean, is it full revs, or the same sort of thing that you get on 1/2 choke?

 

When you start the saw - full choke, the saw fires and dies. Then do you move it to half choke, start it - at this point it'll rev high, but squeezing the throttle briefly should return it to idle.

 

What happens when you just blip the throttle? How long does it take before it cuts out?

 

The MS250 has that sort of semi-circular air filter that just clips on doesn't it? I can't remember about the carb on this saw - but could it be that the atmospheric vent on the carb is blocked?

[gazzapowells]

nothing wrong with breather...

 

thanks every one for advice

 

could be the fuel tank breather needs cleaning, sounds like it could be restricting flow of fuel when the saw starts which would cause it to act as described.

 

After it you have tried starting it a couple of times open the filler cap slowly and see if it sucks air inwards (although this probably isnt so easy on those horrid flappy type fillers)

[DriveLink]

hi

 

saw is started on full choke then move it to 1/2 choke... when it starts revs up about normal for 1/2 choke but when you blip throttle it cuts out...

if dont touch throttle runs for about 10 secs at most!

 

and yes the ms has the filter wish just clips on...

 

 

thanks

 

Hmmm, from the sound of this it could be a couple of things really - starting from the easiest onwards...

 

1) the carb just needs setting up again - in particular the 'L' adjuster (although I really can't remember what access you have on these saws to the H & L settings). Reset H & L to manufacturers recommendations, then adjust 'L' until you find peak revs at tickover - then backoff about 1/4 turn. Take the chain brake off and make sure the chain is not moving (if it is, adjust the LA - idle adjust - screw). You may need to re-adjust 'L' after that. Make sure you make any adjustments with an air filter that's been cleaned.

 

2) It may be that there's too much fuel being shifted within the carb - perhaps the needle in the metering chamber is worn or not seating correctly, or one of the diaphragms is on the way out?

 

3) You may have some sort of blockage in the low speed jet - or rather the tiny holes in the venturi that allow fuel to pass in to the airstream - if that's the case then you'll have to take the carb off and give it a really good clean.

 

I'm just about to start a 7-part series on carburettors over at http://drivelink.blogspot.com on the 1st August - perhaps there'll be a little nugget of information in there to help you!?

[Mesterh]

As you may have guessed there are quite a few different things it could be and its hard to diagnose a fault when you havent got the saw with you.

 

Is it a new saw? ie did you buy it second hand and it was like this?

 

Sounds like fuel starvation or an air leak. which just about sums up all running problems on all chain saws

If you havent taken a carb apart before wait untill Drivelinks info is up or you might just end up buying a new one when you loose a spring or destroy a diaphram.

[Ian150482]

You may have a blockage in the fuel line. when you fill with fuel in this job, doesnt matter how careful you are, crap still gets in fuel tank.

 

Let us know how you get on.

[DriveLink]

So whats happening with this saw then - let us all know!