I have three MS250's, freshly rebuilt, with new Caber I-cast rings, and they all do just like you said. Smooth as silk without the plug, but put the plug in even half-way and it's a struggle.
Stihl ms 250 problem
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I have three MS250's, freshly rebuilt, with new Caber I-cast rings, and they all do just like you said. Smooth as silk without the plug, but put the plug in even half-way and it's a struggle.
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I am not sure who I am responding to at this point.
But in general, excess carbon is a good possibility, as well as flooding/hydrolock, and/or flywheel timing.
But the flooding and timing can easily be ruled out....
But in general, excess carbon is a good possibility, as well as flooding/hydrolock, and/or flywheel timing.
But the flooding and timing can easily be ruled out....
How do we rule out the flooding/hydrolock and/or flywheel timing?
It seems there are several of us having similar / related problems with MS-250's that are extremely hard to pull.
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Well, drain the fuel tank, and take the plug out and pull the rope a whole bunch of times. Let it sit out in the sun a while, pull a bunch more, etc.....
Until you are absolutely sure that the system is totally dry. Then put the plug back in and pull the rope just as if you are trying to start it, but there is absolutely no fuel in it at all.
If the jerking problem is gone, then your problem is there.
If not, then it is not the problem.
Until you are absolutely sure that the system is totally dry. Then put the plug back in and pull the rope just as if you are trying to start it, but there is absolutely no fuel in it at all.
If the jerking problem is gone, then your problem is there.
If not, then it is not the problem.
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Then, to rule out the timing issue, just unplug the plug wire, and again try to start it, as you would if the plug wire was on.
If the flywheel timing was the problem, then it wouldn't yank then...
If the flywheel timing was the problem, then it wouldn't yank then...
Mine turns freely with the plug out and there's no liquid gushing out of any of the orifices like there would be if it was full of gas. It still pulls hard when the ignition is OFF. It's not kickback. (I know what kick back is from dirt bikes- I used to show off by kick starting my Maico 490 in sneakers until the one time it kicked back).
If I did the math right a .2mm layer of carbon on the piston would cause about a 10% increase in compression ratio. Mine got a lot harder to pull relatively suddenly, like over a tank of gas. It feels like way more than 10% harder but there's not that much carbon on the piston.
If I did the math right a .2mm layer of carbon on the piston would cause about a 10% increase in compression ratio. Mine got a lot harder to pull relatively suddenly, like over a tank of gas. It feels like way more than 10% harder but there's not that much carbon on the piston.
For mine, I'll have to wait for some better weather to play with it....thanks for the thoughts. If I learn anything I'll post.
usmcbuckwild
ArboristSite Operative
Once you get the top of the piston cleaned (some diesel or a good quality gun cleaner on a q-tip works well) take a few minutes and clock your sparkplug. Ideal place for the spark plug to fire is towards the most open portion the cylinder. Looking at that picture I would assume the plug is pointing straight down (the opening of the plug ground strap). The initial ignition of fuel isn’t typically the hottest which is leaving the carbon buildup in 1 area on the piston. If you can clock the plug 180* it will fire into the open portion of the cylinder and SHOULD produce less carbon.
Easiest way to clock a plug is to mark where the OPEN end of the ground strap is on the ceramic. This way when you thread the plug in you know where it is pointing.
Easiest way to clock a plug is to mark where the OPEN end of the ground strap is on the ceramic. This way when you thread the plug in you know where it is pointing.
PhilKawasakiuser
ArboristSite Operative
Be careful with that stuff. Don't want a crankcase full of the carbon mess. It was made only to be used on 4mix engines which have a sealed crankcase. Remember 2 strokes have a vented one meaning the leftover mess can end up going around the piston into the case instead of out the exhaust port.
Good advice. I was looking for it to use in disassembled engines to make it easier to remove carbon deposits from exhaust ports and combustion chambers. I agree that the type of application it was marketed for would not be appropriate for assembled 2 cycle engines.
Seafoam
Got plenty of it, add it to non-ethanol gas along with Stabil. So what do you do, soak parts in it straight?
You ever checked the hard to crank over actual compression with accurate gauge?
If the compression is less than 150 it should crank over ok. (my MS250 has 145 compression and cranks over ok)
and I noticed some 250's engine blocks had provision for a compression release (and some don't have the port for such) and some may have that port hole plugged.
Was the compression release optional or???
If the compression is less than 150 it should crank over ok. (my MS250 has 145 compression and cranks over ok)
and I noticed some 250's engine blocks had provision for a compression release (and some don't have the port for such) and some may have that port hole plugged.
Was the compression release optional or???
Konrad
New Member
ok, I’ve had this saw for about 7 years and did never had had any trouble. i didn’t run it at all last year and same thing happened to me, it’s almost impossible to pull. I took exhaust and carb off, same thing hard as heck to pull. Only taking out the spark plug out lets it spin freely. I took a look at the cylinder, it’s clean as a whistle, no build up. I know I’ll beak the rope and/or handle soon. This is unreal. Someone out there please help me before I throw thing dam thing into the fire and never get Stihl again.
thanks for any help.
Konrad
thanks for any help.
Konrad
SteveSr
Addicted to ArboristSite
These saws just do this. This model is the largest displacement in this footprint. They tend to have high compression combined with a small starter pulley which makes it harder to start.
This also makes them easier to flood as well. On a cold start it is hard to get them to "pop". The secret is when it rips the cord out of your hand just take the choke off and pull until it starts.
Have you tried a different carburetor? Wondering if it may create a slightly rich start condition when hot, resulting in a little pre ignition....Just a guess..Also, I think that drop starting a saw works a lot better than trying to start it from the ground, at least one that tends to kick..
I wish I could have all these so called "hard to pull" 250s at my house. I could get this problem solved right away. If it was a wimpy "starter" (owner) then I would steer him towards a sissy saw like the Husky 235 with spring action in the starter. If it was technique then I would help with that also. If it is indeed high compression then we would lower it a tad. And if it was kicking back because of advanced timing, we could fix that too. Quityourbellyach'in
Then there's also the Stihl 251C that I acquired from an estate sale. You can get these with speing-loaded stater assist device that helps make it a piece of cake to turn over when cold. About $400 new, but some say it's worth it. Others say it's another invention getting ready to break down and repair.
The MS250 is notorious for being hard to pull. As stated above, it is because it is the largest displacement in its series and has the same diameter starter pulley as the smaller saws. I have noticed this with all my 025/MS250's. It may help by pulling it slowly to TDC and then giving it all you've got.
I have several Stihl saws that are that way. The latest one I've tried is my MS280 which has sat for a couple of months and is now really hard to get going. For some reason you can take the plug out and spin it over a few times then put the plug back in and it makes it easier to start. I'll try that this week on this one since we're not supposed to go anywhere...
