MS 250 Recoil Sporadically Locking

[GatorBait]

FINAL UPDATE: Went out after wor k to tinker. I tried the upside down technique that Pioneer suggested. After I put the plug back in, I pulled it a bunch of times and it pulled smooth, but didn't start. Put on choke, still pulled smooth, I'm starting to think I fixed it. But it still didn't start. So put back in run position and pulled more... it started to fire! But on about the 3rd pull after it started to fire, it started to lock up again. NOOOO!!! So I know I can temporarily fix this by taking the plug out, and pulling. So I did that. Plug back in, same thing, still didn't fire. Repeated process. Probably happened again. This saw is so close to starting, and I just wanted to start it again. So I decide to go for broke. I'm going to one hand start it, while giving it some throttle. If I tear something up, oh well. So I one hand start it, other on the throttle, and it fires up!! Decent smoke at first... but runs really good at high RPM. Still stalling and flooding out at low RPM. I stall it. Decide I'm going to try to adjust the carb. Now I know nothing about which screw to turn, and which way. Remember, I'm just some idiot with YouTube. But I know the case was marked 1/4 on the L screw, and that seems abnormal. So I start with the low screw and start to open it up. Guess what? The more I open it, the better it runs. Ultimately, I probably ended up with it open about 3/4, the same as every other 250 I've worked on! And now the saw it running great at high RPM, revving nicely, but idling nicely too. Case closed!!

I still don't know whats with the locking. But it doesn't lock on choke. And doesn't seem to lock if its in the run position while giving it throttle. And most importantly, thats how it starts up! So I think I'm comfortable selling this saw now. It does run great. I paid $100, I bought a $5 pawl... and I think I'm going to get $225 for it based on prior sales. And more importantly, I got a little more experience with carbs, and maybe learned something about what to do with the locking... give it throttle. Thanks to you all for your input and suggestions!

 

[ChuckMI]

"When I take the spark plug out, it pulls over beautifully. The issue is only with the plug in. I've also noticed that when the choke is on, the saw still pulls over beautifully. Its only when I put it in the "run" position that I start to get that super hard hesitation. Its enough that it will maul the pawl if you keep doing it."
Mine has been like that for 20 years, since it was new. It is a standard feature on the MS250. I put a D-handle on the pull cord so I could keep a better grip on it. Mine hasn't damaged the pawl.

 

[Okie]

I had a MS250 awhile back that had strange symptom similar to yours.
It was given to me for parts, looked almost new with bar and chain. Had more than the normal hard pull issues erratically.
Sometimes erratically the pull rope would get hard to pull but I could with care pull it past the hard spot and eventually maybe start the saw.
I took the spark plug out and removed the recoil and I started turning the flywheel slowly by hand to see if I could feel any hard spots. It eventually indicated a hard spot going in the same direction that the pull rope pulls the flywheel. I could reverse the flywheel little bit easily and then go the other way and feel the hard spot again usually. I could back the flywheel up about 1 turn and then go right direction it would eventually hit the hard spot again as the flywheel was turned by hand. Sometimes it would eventully hit the hard spot going backwards. What was happening was the roller bearings was catching and sliding instead of rolling on broken plastic pieces of the wimpy plastic bearing separators inside the roller bearing race.

Long story short, when I open up the clam shell case the plastic wimpy crankshaft bearing's separator's was broken into several small tiny pieces and they would eventually cause the bearings to slide in their race instead of roll and the bearings by not being equally spaced would allow some up down slack on the crankshaft. Almost time for the saw to destroy itself.

I replaced the bearings with the all metal type bearings and the saw ran like new.
I used Yamaha Bond 4 to seal the clam shell case back together together with good results. I let the Yamaha Bond 4 cure for 24 hours before starting the saw.

I like Stihl chainsaws, but the 250 series is not one of my favorite saws. I just cannot recommend that anyone buy a 250 series Stihl. (Stihl should be ashamed of themselves when they designed the 250 series of saw)
I always bring a 250 up on the compression stroke then pull through with a stout shoulder pull. They just pull crank harder than my other Stihls even when all is right..

Caution: Playing with chainsaws (all kinds) has a way of getting into your blood.

 

[GatorBait]

I had a MS250 awhile back that had strange symptom similar to yours.
It was given to me for parts, looked almost new with bar and chain. Had more than the normal hard pull issues erratically.
Sometimes erratically the pull rope would get hard to pull but I could with care pull it past the hard spot and eventually maybe start the saw.
I took the spark plug out and removed the recoil and I started turning the flywheel slowly by hand to see if I could feel any hard spots. It eventually indicated a hard spot going in the same direction that the pull rope pulls the flywheel. I could reverse the flywheel little bit easily and then go the other way and feel the hard spot again usually. I could back the flywheel up about 1 turn and then go right direction it would eventually hit the hard spot again as the flywheel was turned by hand. Sometimes it would eventully hit the hard spot going backwards. What was happening was the roller bearings was catching and sliding instead of rolling on broken plastic pieces of the wimpy plastic bearing separators inside the roller bearing race.

Long story short, when I open up the clam shell case the plastic wimpy crankshaft bearing's separator's was broken into several small tiny pieces and they would eventually cause the bearings to slide in their race instead of roll and the bearings by not being equally spaced would allow some up down slack on the crankshaft. Almost time for the saw to destroy itself.

I replaced the bearings with the all metal type bearings and the saw ran like new.
I used Yamaha Bond 4 to seal the clam shell case back together together with good results. I let the Yamaha Bond 4 cure for 24 hours before starting the saw.

I like Stihl chainsaws, but the 250 series is not one of my favorite saws. I just cannot recommend that anyone buy a 250 series Stihl. (Stihl should be ashamed of themselves when they designed the 250 series of saw)
I always bring a 250 up on the compression stroke then pull through with a stout shoulder pull. They just pull crank harder than my other Stihls even when all is right..

Caution: Playing with chainsaws (all kinds) has a way of getting into your blood.

Okie,

Thank you for sharing all of this. In a perfect world I'd dive this deep into saws. And maybe in retirement, I will. But for now I work 40 hours running a bank, and am a husband and a father. I can sneak in 30-45 minutes in the evening after work to tinker. But I try to limit that to rebuilding carbs. I've now added recoil replacemnt and sprocket replacement to my repitoire. But I dont think I'm ready to get that as deep as your describing yet! But yesterday I picked up 2 250's for $125 ($62.50 each saw!). I already have them running. They just need a bar and chain and I'll be selling them for $225, maybe more! At some point I may buy a saw I can't fix... but so far I've made money on all my saws. So if one day I take a loss I'll still be ahead! Thanks!

 

[Okie]

You say:
But I try to limit that to rebuilding carbs. I've now added recoil replacemnt and sprocket replacement to my repitoire.

We understand.
(MAGNUM FORCE, Eastwood, "A man's got to know his limitations")
You tube (with a grain of salt) and this forum is good for getting in deep.
I also dreaded opening up the 250 but you will find the clamshells types are easy to work on.
Several of the same type saws are a good thing for parts, sometimes take two or three and make one.
Most of the cheaper Poulans are also clam shells and good for experience. (and to accumulate for parts, take 5 or 6 of them and make 1/2 of one and keep your BANK money in your pocket.

Just curious, Where do you find (locate) most generally your saws for fixing and flipping?

 

[GatorBait]

You say:
But I try to limit that to rebuilding carbs. I've now added recoil replacemnt and sprocket replacement to my repitoire.

We understand.
(MAGNUM FORCE, Eastwood, "A man's got to know his limitations")
You tube (with a grain of salt) and this forum is good for getting in deep.
I also dreaded opening up the 250 but you will find the clamshells types are easy to work on.
Several of the same type saws are a good thing for parts, sometimes take two or three and make one.
Most of the cheaper Poulans are also clam shells and good for experience. (and to accumulate for parts, take 5 or 6 of them and make 1/2 of one and keep your BANK money in your pocket.

Just curious, Where do you find (locate) most generally your saws for fixing and flipping?

Thanks Okie. I buy everything off of Facebook Marketplace. Lately its been a lot of 250s. I've paid as little as $62.50 (this past weekend) or as much as $225. But if its a mint 250 with the manual and a case... I can sell it for $300. And I'll go pickup a saw to make $75! I recently bought a pretty nice and running fine 391 for $300. It's listed for $500... nothing yet, but I'm sure I'll get $400 minimum, hoping for $450.

 

[pioneerguy600]

FINAL UPDATE: Went out after wor k to tinker. I tried the upside down technique that Pioneer suggested. After I put the plug back in, I pulled it a bunch of times and it pulled smooth, but didn't start. Put on choke, still pulled smooth, I'm starting to think I fixed it. But it still didn't start. So put back in run position and pulled more... it started to fire! But on about the 3rd pull after it started to fire, it started to lock up again. NOOOO!!! So I know I can temporarily fix this by taking the plug out, and pulling. So I did that. Plug back in, same thing, still didn't fire. Repeated process. Probably happened again. This saw is so close to starting, and I just wanted to start it again. So I decide to go for broke. I'm going to one hand start it, while giving it some throttle. If I tear something up, oh well. So I one hand start it, other on the throttle, and it fires up!! Decent smoke at first... but runs really good at high RPM. Still stalling and flooding out at low RPM. I stall it. Decide I'm going to try to adjust the carb. Now I know nothing about which screw to turn, and which way. Remember, I'm just some idiot with YouTube. But I know the case was marked 1/4 on the L screw, and that seems abnormal. So I start with the low screw and start to open it up. Guess what? The more I open it, the better it runs. Ultimately, I probably ended up with it open about 3/4, the same as every other 250 I've worked on! And now the saw it running great at high RPM, revving nicely, but idling nicely too. Case closed!!

I still don't know whats with the locking. But it doesn't lock on choke. And doesn't seem to lock if its in the run position while giving it throttle. And most importantly, thats how it starts up! So I think I'm comfortable selling this saw now. It does run great. I paid $100, I bought a $5 pawl... and I think I'm going to get $225 for it based on prior sales. And more importantly, I got a little more experience with carbs, and maybe learned something about what to do with the locking... give it throttle. Thanks to you all for your input and suggestions!

When you are giving it throttle you are essentially giving it more air, the throttle plate in the carb is partially or fully open thus letting more air in to help dry up the excessive fuel already in there. The method I and many others use to start a wet or flooded saw is to open the throttle. Some of the Stihl saws have built in stops that hold the throttle a bit open, by pushing the control lever down to set the choke and then before pulling it over lift the control lever up one notch but only one notch, that will give the engine more air, that is what it needs to start up. I have on occasion put a tie wrap around the rear handle and across the throttle trigger cinched up tight ,thus letting the carb get more air on saws without the built in stop, this speeds up the starting. The cure for all this is to stop the carb from letting fuel seep past the inlet needle in the carb, sometimes parts replacement is enough but other times the seat is damaged or there is foreign material like varnish built up on the seat, there are times I have cleaned the seat off enough by using toothpaste on a round tooth pick . I have wood picks that are just a tad over 1/8" dia that work for this cleaning, rotate them with a battery drill til it cleans the varnish or stuck on dirt off the seat and the needle seats and stops the fuel from seeping past. Not every carb has been successful though, those with high hours on them can have an ovaled out seat shape and the cleaning won`t fix that, then it has been a carb replacement .

 

[GatorBait]

When you are giving it throttle you are essentially giving it more air, the throttle plate in the carb is partially or fully open thus letting more air in to help dry up the excessive fuel already in there. The method I and many others use to start a wet or flooded saw is to open the throttle. Some of the Stihl saws have built in stops that hold the throttle a bit open, by pushing the control lever down to set the choke and then before pulling it over lift the control lever up one notch but only one notch, that will give the engine more air, that is what it needs to start up. I have on occasion put a tie wrap around the rear handle and across the throttle trigger cinched up tight ,thus letting the carb get more air on saws without the built in stop, this speeds up the starting. The cure for all this is to stop the carb from letting fuel seep past the inlet needle in the carb, sometimes parts replacement is enough but other times the seat is damaged or there is foreign material like varnish built up on the seat, there are times I have cleaned the seat off enough by using toothpaste on a round tooth pick . I have wood picks that are just a tad over 1/8" dia that work for this cleaning, rotate them with a battery drill til it cleans the varnish or stuck on dirt off the seat and the needle seats and stops the fuel from seeping past. Not every carb has been successful though, those with high hours on them can have an ovaled out seat shape and the cleaning won`t fix that, then it has been a carb replacement .

Pioneer,

This makes a lot of sense. I'm learning... learning what things I seem to see over and over, and then learning the workarounds!

 

[pioneerguy600]

Pioneer,

This makes a lot of sense. I'm learning... learning what things I seem to see over and over, and then learning the workarounds!

Keep at it and you can learn a good deal just working on them, I worked on my first chainsaw way back in 1959 and by 63 I was working in a dealership repairing Pioneer saws, since then I have continuously had saws in my hands. Not to mean every day but many days per year.

 

[ZeroJunk]

Most screws on these saws, or nuts, are 5mm .8 .
There are a few 4 mm screws on the ignition modules , etc.
Be careful with those because you can strip them with a battery powered nut driver pretty easily.
And, larger saws have some 6 mm on the cylinder and muffler. Don't know the pitch on those off the top of my head. Sorry.
Everything on the MS250 in to metal will be 5 MM .
Everything is lefty loosey but the clutch.

Should clarify. The screws that hold the pan on are some odd self tapping.
And, a lot of the screws are course thread in to plastic screws.

 

[Coralillo Lo Pro]

Tree service guy keeps bringing me his MS250 to fix because his guys break the starting cord, break the pawls... I told him it's legendary for seeping fuel and locking and to pull the plug any time it's difficult or hold the throttle down while starting. I have an MS361 that's sticky that way too but not as bad, and it at least has a decomp valve. The MS250 is one of the only 45cc saws ever built that could use a decomp valve due to this common problem.

 

[Oletrapper]

When you are giving it throttle you are essentially giving it more air, the throttle plate in the carb is partially or fully open thus letting more air in to help dry up the excessive fuel already in there. The method I and many others use to start a wet or flooded saw is to open the throttle. Some of the Stihl saws have built in stops that hold the throttle a bit open, by pushing the control lever down to set the choke and then before pulling it over lift the control lever up one notch but only one notch, that will give the engine more air, that is what it needs to start up. I have on occasion put a tie wrap around the rear handle and across the throttle trigger cinched up tight ,thus letting the carb get more air on saws without the built in stop, this speeds up the starting. The cure for all this is to stop the carb from letting fuel seep past the inlet needle in the carb, sometimes parts replacement is enough but other times the seat is damaged or there is foreign material like varnish built up on the seat, there are times I have cleaned the seat off enough by using toothpaste on a round tooth pick . I have wood picks that are just a tad over 1/8" dia that work for this cleaning, rotate them with a battery drill til it cleans the varnish or stuck on dirt off the seat and the needle seats and stops the fuel from seeping past. Not every carb has been successful though, those with high hours on them can have an ovaled out seat shape and the cleaning won`t fix that, then it has been a carb replacement .

One other thing that can be done is crack the fuel cap to relieve tank pressure before trying to start. jmho OT

 

[GatorBait]

Keep at it and you can learn a good deal just working on them, I worked on my first chainsaw way back in 1959 and by 63 I was working in a dealership repairing Pioneer saws, since then I have continuously had saws in my hands. Not to mean every day but many days per year.

Thank you Pioneer, I'm enjoying it as a hobby!

 

[GatorBait]

Tree service guy keeps bringing me his MS250 to fix because his guys break the starting cord, break the pawls... I told him it's legendary for seeping fuel and locking and to pull the plug any time it's difficult or hold the throttle down while starting. I have an MS361 that's sticky that way too but not as bad, and it at least has a decomp valve. The MS250 is one of the only 45cc saws ever built that could use a decomp valve due to this common problem.

This makes a lot of sense. And now I'm noticing my personal saw, which is "mint" (also a 250) was doing it too. Given all this feedback, this seems "normal" for this model. Will just keep using throttle to start it, which will be better on the saw recoil, but its good to know its not a symptom of a failing saw (aside from s tiny carb issue)!

 

[GatorBait]

One other thing that can be done is crack the fuel cap to relieve tank pressure before trying to start. jmho OT

I haven't done that yet, but I should... because when I do after running it, you always get that pop, so I should add that to things I do, thanks!

 

[pioneerguy600]

Thank you Pioneer, I'm enjoying it as a hobby!

One thing you can do is set a tiewrap on the rear handle around the throttle trigger and just have it there when needing it to start the saw, it can be slipped back off when the saw starts and can be left there forever if needed, just slip it forward over the trigger any time needed and slip it off after starting. The pressure in the tank caused by fuel mix expansion seems to be getting worse all the time and it takes a very tight fitting fuel needle to seat in the carb. I am fighting this issue right now with a few different model of saws, a couple of my 044`s and one of my 026`s are displaying these wet cylinder symptoms, they have high hours on them and will get new OEM carbs if I cannot cure the leakage. The older carbs like the Tillotson HL models had replaceable seats in the carb, not like today`s throw away designs.

 

[ZeroJunk]

I was thinking, dangerous I know, that the older tank vents would let the pressure out.

Can't imagine a fuel line with a screw in it allowing a lot of tank pressure.

Anyhow, seldom have a hydrolocked saw, but 2 cycle blowers, it's almost daily.

And, If I don't replace the carb they will come right back with the same issue.

 

[Old2stroke]

This makes a lot of sense. And now I'm noticing my personal saw, which is "mint" (also a 250) was doing it too. Given all this feedback, this seems "normal" for this model. Will just keep using throttle to start it, which will be better on the saw recoil, but its good to know its not a symptom of a failing saw (aside from s tiny carb issue)!

I hope you are clear on the difference between full throttle starting to clear any flooding issues and fast idle setting of the throttle for "normal" cold starting. Gone are the days when saws had a throttle lock button on the rear handle that could be engaged to hold the throttle partly open for cold starting, it was easy to use and everyone understood it, now we have saws with the fast idle interlocked with the choke and MANY of my customers do not understand how to set fast idle with no choke. A cold chainsaw is VERY difficult to start with the throttle closed and most of the "hard to start" issues are because the owner is trying to start with the throttle closed.

 

[ZeroJunk]

Be careful if you want to drop start saw with the throttle held wide open. Good way to cut your leg off.
I do it sometimes with a smaller saw, but I take the bar and chain off. Eventually they will clear out.

You can take an air compressor and blow through the spark plug hole. Bad enough it will puke it out the muffler.

The issue with the 025 and the MS250 has always been the radius of the starter pulley for the displacement of the saw.
They have no magical compression.
People let them get dry and bring them in "locked up" with some regularity. And, with some regularity we sell them a battery powered saw.

In general I would estimate that at least 75 % of the stuff we get that says "won't start" there is nothing at all wrong with it.

Either flooded, or they didn't pull it enough to get the fuel up, or they just can't pull one anymore.

Then there is always the one that you pull the rope and say "aw ****" and it's scored all to hell.

 

[GatorBait]

Be careful if you want to drop start saw with the throttle held wide open. Good way to cut your leg off.
I do it sometimes with a smaller saw, but I take the bar and chain off. Eventually they will clear out.

You can take an air compressor and blow through the spark plug hole. Bad enough it will puke it out the muffler.

The issue with the 025 and the MS250 has always been the radius of the starter pulley for the displacement of the saw.
They have no magical compression.
People let them get dry and bring them in "locked up" with some regularity. And, with some regularity we sell them a battery powered saw.

In general I would estimate that at least 75 % of the stuff we get that says "won't start" there is nothing at all wrong with it.

Either flooded, or they didn't pull it enough to get the fuel up, or they just can't pull one anymore.

Then there is always the one that you pull the rope and say "aw ****" and it's scored all to hell.

I really prefer to start my saws on the ground, one foot in the handle. Some of these have felt like they needed throttle though. I can one hand start a 250... but if/when I do, I'll try to pub the brake on. But now I think I'm taking the choke too far off... and I'm just starting it in regular idle, which is what's needing that throttle. But if I just click the choke barely back... its still open some... and I can pull it on the ground and still get that effect of throttle and an easier pull. This may make no sense, but it does in my head! For my mint/new 291, its like 2 pulls on choke, it starts to fire. I squeeze the throttle, the chock level disengages... then I pull it again, and it fires up, but its still under throttle... I squeeze the throttle again and it goes into the idle position. I think I'm manually moving the choke lever to the idle position which may be why I'm getting the lock in the recoil, and also finding I need throttle to start it. I'm doing it wrong. Again, apologies if this makes little/no sense.