Stihl MS 250 Chain Saw Problems

[Slider99]

Is it losing prime? Have the fuel lines, fuel tank grommet, and primer bulb been replaced?
Has the spark arrestor screen been cleaned?
Was a new spark plug installed?
I'm willing to bet that the shop didn't do a thorough evaluation.
Aftermarket ignition modules aren't the best.

These don't have primer bulbs

 

[platefire]

As previously said, it worked fine last time I used it. I haven't got around to firing it up again. Thanks for everyone's comments.

 

[rhkraft]

You might try replacing the fuel tank filter. My Stihl was hard starting and once it was running it would fail when I tried to accelerate the engine. A new tank filter fixed everything. Another thing I learned. My Stihl was running good, but after a while it idle and stumble and sometimes quit. I began to notice that it ran well on a full tank of fuel and only ran poorly after about half the fuel was gone. I found a crack in the tank fuel line. When the tank was full, the crack was under the fuel level. But once the crack was exposed to the air, it started sucking air starving the engine for fuel. Another useful tidbit.

 

[platefire]

This morning I got my Stihl out for a crank test. Pulled 4 times in the full choke position then switched to the half choke position. Pull it about
6 times and it fired up. It ran real strong with quick responsive acceleration. I shut it down before I ever got to the run position. Remember
this saw don't have a prime bulb. So I surmise it could of cranked a little quicker. It still has the original plug, so a new plug might be worth a try
for improvement. Need to switch to Ethanol free gas and drop the Lucus. Maybe I can nurse it back to good health:>)

 

[slomo]

E-0 yes if you can find it but why 91 octane?

Chainsaws have a ton more compression than say push mowers. Some trimmers like my Commercial Maruyama need a seasoned shoulder to pull over as well.

 

[slomo]

I'm not familiar with Opti-2 Oil?

It's the best 2 stroke oil on the market. Even has stabilizer in it. Running it for years. Much less smoke and carbon buildup compared to Echo and Stihl oils.

My Maruyama trimmer was bought in 2013. Pulled the muffler. Bore was pristine with zero scratches our gouges. Very very minimal carbon was visible.

 

[Hammermechanicman]

Chainsaws have a ton more compression than say push mowers. Some trimmers like my Commercial Maruyama need a seasoned shoulder to pull over as well.

I have 5 chainsaws. 2 of which are running high compression and advanced timing. If you try to start them without using the compression release they break starter pawls. I run regular gas in all of them with zero issues. All the internet mechanics quote the Stihl manual but i am still waiting for someone to show me a saw damaged from preignition from regular gas I put it in the same category as "starting fluid will blow your engine up" crowd. Internet wives tale with no proof.

 

[slomo]

200psi comes out to 13.6:1 static compression. That is pretty high. Aluminum block/head helps cool the cylinder.

From the MS 250 manual below. Stihl recommends a minimum 89 or higher octane.

"

 

[Hammermechanicman]

200psi comes out to 13.6:1 static compression. That is pretty high. Aluminum block/head helps cool the cylinder.

From the MS 250 manual below. Stihl recommends a minimum 89 or higher octane.

"View attachment 71410

Stihl recommends because it needs it or is that just corporate covering their ass documentation??? I have worked on hundreds of saws over the years and pretty much all running regular gas and i have never seen a saw with preignition damage.

 

[slomo]

Stihl recommends because it needs it or is that just corporate covering their ass documentation??? I have worked on hundreds of saws over the years and pretty much all running regular gas and i have never seen a saw with preignition damage.

200psi is up there. I would say it needs it. 89 octane is a bare minimum at that.

Just follow the manual. Why risk it?

Would suck running another fuel can just for a saw but, some of those saws ain't cheap.