MS250 start compression relief stopped working

[CedChop]

I have an MS250 about 3 years old with about 50 hours on it. Has been great so far. Glad I spent the money
However, this year when I go to start it the pull is extremely hard. As a matter of fact it is so
hard that I have to put it on the ground hold it down with my foot and when I pull it can jerk it
out of my hand pinching my hand against the saw body, ouch....If I go ahead and pull it thru a few
cycles I can get it started and it runs fine.

I removed the spark plug to see if oil or something is filling the cyllinder but nothing there. I thought
maybe its just sparking early but even with no spark the pull is extremely hard.

To start it I pull thru the first TDC and the 2nd TDC with a lot of pull fight several times
it will finally start.

Since it was very easy to pull and start before I am thinking that it may have some kind of automatic
decompression valve that closes after it starts. Maybe this valve is now stuck.

At this point I can't even remember how difficult it was to pull when new.

Any ideas?

Makes me wonder if my old pullin saw may have to come to life.

 

[Bubster]

It cranks normal without the spark plug in it?

 

[CedChop]

It cranks normal without the spark plug in it?

yes it does, so no problem with rope, crank, pull mechanism.

 

[CedChop]

there was a similar posting about a larger saw that mentioned that bar chain oil can get back into the crankcase and I thought that was the problem until a posting mentioned that the ms250 is a clamshell design so that wouldn't happen. but...I wonder whatever pumps the oil out could lead back into the cylinder somehow? It feels like that, a heavy oil coating inside the cylinder making compression very high.

 

[ericm979]

The MS250 does not have an automatic compression release. I don't know of a two stroke saw that does. I think there's a four stroke chinese saw with one.

The MS250 and earlier 025 (same saw but with screw caps) is known for this. My 025 did it. Part of the problem is the pull start pulley is small for the engine displacement, making it hard to start for its size to begin with. But there's also a mysterious increase in starting effort that sometimes happens. Others here have had it happen. One theory is carbon buildup on the piston crown and combustion chamber. Why that appears to happen suddenly is a mystery but may be more due to human perception than something mechanical.

 

[Bubster]

Yes you have to have a camshaft for an auto decomp to work. My only problems with an 025/250 not cranking over easy has always been the fuel metering valve letting too much fuel in. Many people complain about the 250 being hard to crank though.

 

[AmateurSawer]

Check your spark arrestor screen.

 

[sundance]

Sounds a lot like my 250 (except the part about implying it was easy to start for 3 years and 50 hours of use). Mines been a beast pretty much from the gitgo. I've been assured i just need to man up and really pull it. RIGHT!
Watching with interest to see if anything comes up. Note there are several threads on here about hard to pull 250s.

 

[Lawless]

No help except these are known to flood, especially after hot and trying to restart. Is it possibly it is flooding after it sits causing it to be hard to pull over?The fix for mine was a replacement Chinese carb to fix the flooding. It is my most used saw now and the pro saws mostly sit. It is not hard to pull over but it admittedly never was before the swap.

 

[dmb2613]

May need a carburetor on it and may have carbon buildup but the 250 is a bear to start sometimes

 

[stihltech]

It is all in the wrist
Seriously, I get this alot with 025/MS250. The starting technique makes all the difference. Pull up tp compression, then pull through. Timing is kind of advanced on these. If you just pull, there is time for the spark too to happen too early and you get kickback on the handle.
Tis is how I start most saws. After 40 years, you learn it hurts the knuckles otherwise.

 

[user 74409]

This is common issue with 025/MS250. I have experienced after saw sat over winter. A recommended starting technique is to pull over slowly 4 or 5 times before pulling hard enough to start.

 

[Okie]

I've bought a really low hour MS250.
I have to bring it up on the compression stroke slow, when I feel it about to pull through I pull hard. Never has been a easy crank. Runs good once started. I think maybe my MS 250 is also the one Stihl that has has the flippy caps that spill gas down your leg if not secured good. Sometimes takes fiddling around to make sure the caps are secure. Not a good thing on a hot day.
Just not a user friendly saw. Thinking of placing a price on it.

I have other Stihls that crank ok.
My 250 does not get used much because I dread trying to start it when removing it from storage.

Hard to believe your 250 was EASY to crank once upon a time.
Would have been curious as to the compression reading when it cranked EASY.

 

[coffeebrk]

I put a D shaped handle on my ms250 and pull it like I'm angry. Much easier to start now. Everyone has different arm and shoulder strength so you have to take that into account also.

 

[duane4238]

Add my name to the list of ms250 users with impossible to start saws. I bought mine new. It was near impossible to start without ripping your fingers off and I'm not a little guy. Took it back to the dealer and it did the same for them. They told me it should get better with use. Went to another dealer and he said I just needed to pull harder. Big help that was. It now has been sitting on the shelf for about 3 years and I've never used it. I have a 192, 270, and a 260 that I can start with no problem and they get used all the time. My 250 is now a garage shelf decoration. A total waste of money. Good luck with yours.
Duane

 

[sundance]

Add my name to the list of ms250 users with impossible to start saws. I bought mine new. It was near impossible to start without ripping your fingers off and I'm not a little guy. Took it back to the dealer and it did the same for them. They told me it should get better with use. Went to another dealer and he said I just needed to pull harder. Big help that was. It now has been sitting on the shelf for about 3 years and I've never used it. I have a 192, 270, and a 260 that I can start with no problem and they get used all the time. My 250 is now a garage shelf decoration. A total waste of money. Good luck with yours.
Duane

Mine still gets occasional use when I decide I'm up for the challenge of starting it. I have gotten better at it but still difficult.
Recently bought an Echo CS-4910 to pretty much replace it. I'm a lot happier with it.
I really should just sell the 250 instead of fighting with it.

 

[coffeebrk]

Add my name to the list of ms250 users with impossible to start saws. I bought mine new. It was near impossible to start without ripping your fingers off and I'm not a little guy. Took it back to the dealer and it did the same for them. They told me it should get better with use. Went to another dealer and he said I just needed to pull harder. Big help that was. It now has been sitting on the shelf for about 3 years and I've never used it. I have a 192, 270, and a 260 that I can start with no problem and they get used all the time. My 250 is now a garage shelf decoration. A total waste of money. Good luck with yours.
Duane

Dust it off and sell it.

 

[CedChop]

This is common issue with 025/MS250. I have experienced after saw sat over winter. A recommended starting technique is to pull over slowly 4 or 5 times before pulling hard enough to start.

I guess I'll have to grin and bear it. The aggravating thing is that it was relatively easy to start when it was new like 50 hrs ago. I am still thinking that somehow chain oil is getting in there. maybe I'll try running it out of chain oil and then see what happens. - I have experienced after saw sat over winter- that is exactly with happened to mine. those flippy fill caps are a pain, one of those german inventions looking for a problem to solve. very sad, I was so proud of owning a stihl instead of my old pullins. shoulda gone echo.

 

[CedChop]

It is not human perception. On that first pull thru TDC it will rip that handle out of your hand. I'll ck that flame arrestor although if that's clogged I'd think that it would not run.

 

[Patrick1903]

I have an MS250 about 3 years old with about 50 hours on it. Has been great so far. Glad I spent the money
However, this year when I go to start it the pull is extremely hard. As a matter of fact it is so
hard that I have to put it on the ground hold it down with my foot and when I pull it can jerk it
out of my hand pinching my hand against the saw body, ouch....If I go ahead and pull it thru a few
cycles I can get it started and it runs fine.

I removed the spark plug to see if oil or something is filling the cyllinder but nothing there. I thought
maybe its just sparking early but even with no spark the pull is extremely hard.

To start it I pull thru the first TDC and the 2nd TDC with a lot of pull fight several times
it will finally start.

Since it was very easy to pull and start before I am thinking that it may have some kind of automatic
decompression valve that closes after it starts. Maybe this valve is now stuck.

At this point I can't even remember how difficult it was to pull when new.

Any ideas?

Makes me wonder if my old pullin saw may have to come to life.

Sorry about your issues with ms250. As others said, it’s a really common problem. I have a ms250 same age as yours, similar hours. Has always been tough to start. Lent it to my father in law (he does a lot more tree work than I do) after his ms260 died. He gave it back to me after a month. Too hard to start.

I think I proposed same solution in last similar thread; Sell Ms250 buy MS261 (or insert alternative saw here). I’m a glutton for punishment and haven’t sold mine yet.