Stihl MS250 hard to pull?

[Jack S]

My little husky 435 got to where I couldn't pull the starter rope anymore and I discovered that the plastic starter pulley  had started to disintegrate one of the tabs that catch the starter pawls on the flywheel. This caused it to bind up somehow.It started out being just harder to pull. After replacing it the saw is now back to a normal starting saw.  Again this is husky. A different design than stihl. 

[Al_Smith]

Well recoils can lead you off 40 ways from  Sunday .The pawls get bent,drums run eccentric even the spring wound so tight you can only get about half a pull . I suppose it could get a large build up of carbon although I've never seen it happen .
I've got some saws I've modified where the piston.head deck clearance was taken from  46 thou to 22 thou and are right at 200 PSI .I'm just a little skinny dude 6 feet tall ,almost 200 pounds with size 11 shoes .Plus I'm nearly 72 years old and I can pull them over with no decomp . I can still bent over and touch my toes so I guess the aging thing hasn't hurt me too bad---so far  8)

[yardiron]

It doesn't have a compression release.
I've had the recoil apart twice, I can't find anything wrong with it.
Like I said before, if I take out the plug, the thing spins over freely, no bind in the rope or engine.
The engine has a ton of compression, a peak down the cylinder with one of those usb cameras shows a clean, slightly gray/tan topped piston. The bore is clean with no scratches. The piston is visible through the exhaust port, the sides are clean, no marks.
Adding oil doesn't change it much, so its not a dry cylinder, adding oil does make it harder to pull if you don't crank it out the cylinder before putting the plug back in.

The recoil rope has obviously been changed, none of the saws I saw at the dealer had black with orange ropes but since I have the spool it came from, and is recoil rope in 3.5mm, I can only assume the original rope broke at some point. The black and orange rope is marked 'Spectra' and Guaranteed Unbreakable. Its got a Stihl part tag on it but no number. I'm guessing my uncle bought it from what ever dealer he was buying from. Likely a JD dealer since he also had several green machines. It feels like normal rope but its black.

If you can manage to yank the rope three times, it starts and runs great, the thing idles perfect, and cuts great. I have used the saw, I like how it handles and feels but I really don't care to deal with a saw that's this painful to start. I can go down to any big box store and pickup a $200 saw to take its place that won't give me this much grief. But in reality, I don't 'need' any of these saws, but since they were free, (inherited), I've sort of added them to my pile of old saws. I just figured that having something newer would be nice rather than running something heavy and 40 years old every time I need to cut wood. I have my 029, and my 036, the 029 is great, its never given me an ounce of trouble after 20+ years. I bought that one new myself. It starts easy, runs great and gets the job done but its a bit heavy for just light yard work. The same for the 036P, its a great saw, much lighter than the 029 but its got a 24" bar and is more for dropping trees than cutting up limbs. The 250 would have made a good small saw to add to my own collection here but if this is as good as it gets, its likely going to sit on the shelf or find a new home. I'll keep using my old Homelite. 

[lxskllr]

Going by what moodnacreek said... Perhaps you could take a little off the top of the piston. You don't like using it now, so the worst that'll happen is you still won't like using it, but you could end up with a saw you really enjoy.

[mrcaptainbob]

This exactly describes my issue with the MS310. EXACTLY! A few days ago I started thinking about maybe it being, as was suggested here, the coil advance being bad. Inspection showed some scratch marks on the flywheel. The coil center post ws at a proper gap, but the 'tail' on the coil appered to be dragging on that high part of the flywheel. Reset the coil airgap to .oo8" and IT STARTED! Was MUCH easier to pull! But it ran really, really bad. Reset the airgap to .006" at the coil pick up and .008 at the coil 'leg' and it's back to it's not-being-able-to-pull-the-rope again tricks. Might have a chance this weekend to fuss with it. Will reset airgap to something else and see if it clears things up. For your saw....maybe verify the airgap and look at possible drag marks on the flywheel...

[yardiron]

Something that was bugging me about something someone said here made me take the recoil back off last night. Someone referred to the recoil 'pawls'. This thing only has one pawl and while there's two holes, the clip that guides the pawl has only one slot?

There's also only 5 notches in the cup it engages, having a second pawl wouldn't matter since it wouldn't align with an opposite notch.

I pulled the muffler again, the dealer kept telling me maybe the crankcase was full of oil, he said to turn the crank by hand till the skirt cleared the port and hang the saw by the handle over night over a pan??
I did that, nothing came out. He also said to make sure the honeycomb wasn't blocked in the exhaust.
This saw has a one piece muffler, it comes off as a unit, not in parts like the larger saws. He said some of these had a ceramic honeycomb in the muffler much like the catalytic converter on a car. Mine has that type of muffler. But, I can freely blow air through the muffler, and it doesn't turn any easier with the muffler removed.

The one thing I did notice is that I can turn the saw backwards past TDC fairly easy, but not forward?
Right now the carb and muffler are off, so the there's nothing restricting it at all. In the direction it runs, if I turn the engine over, from the point the rings clear the exhaust port, it gets nearly impossible to turn unless the plug is out.
Now, if I rotated it in reverse, again to the same point, I can turn it past TDC with my hand simply on the flywheel.
While I realize there's timing issues with the ports and all, in either direction the piston is still compressing the same volume of air once its above the open ports. Yet in reverse, it turns with normal effort, yet forward, I need to use a breaker bar. With the plug out, it spins freely in either direction.

I realize too that as a motor breaks in, it likely can gain some compression, but this thing doesn't look like its reached its full break in point yet as there's no pattern showing on the piston or cylinder yet. If its going to gain even more compression, I can't imagine how much it'll need to pull the rope.

Something I notice is that when turning it by hand against the compression, it seems to have 'zero loss'. On most engines, as you hold it against the compression stroke, it will slowly dissipate pressure from natural losses past the rings, but this never does. What ever air is trapped above the ports stays there, if I lock it at TDC, leave it sit there for an hour, when I come back and loosen the spark plug it still under pressure. I don't know if this tells me anything but its something I couldn't help but notice so I had to check to see how long it held pressure. With this in mind, I don't see how it can ever be improved short of it losing some compression.
With the piston all the way down, I can see clearly to the top of the combustion chamber and its spot clean, no carbon at all. The top of the piston is the same way, with only minimal coloration from being run.


There are no drag marks on the flywheel, the coil isn't dragging, the motor spins nice and free with the plug out. I've even removed the coil to eliminate any magnetic effect but the resistance isn't coming from the coil, its coming from compression.

Like I said before, the saw runs great, if you can manage to pull the rope.
Its pretty much impossible to do without a glove on, my bare hand cannot grip the handle tight enough to pull the thing.
Even if I get it past the first TDC, the second one hits my wrist like a ton of bricks and stops the rotation.

Something I did notice is that it don't take much to make the rope hard to pull.
with the muffler and carb still off, the ignition coil pulled back, and the plug out, if I put my finger over the plug hole, even lightly, the compression becomes pretty severe and the rope gets hard to pull. Although I can't hold back the compression with my finger, my finger over the plug hole is enough to make the rope hard to pull?

I've tried another recoil assembly, the dealer gave me one he had laying under the bench. Its no different than the original recoil.

I retested the compression with the carb and exhaust off, with some light oil lubing the cylinder up shot in from the sides.
If I clamp the saw to the bench and pull the rope with a gloved hand I get between 200 and 245 psi.

How much compression is normal? They all can't be like this, they wouldn't have sold so many of these.

I'm getting close to just putting it together and selling it, let someone else deal with it.
After all, it runs great if you can get past the pain of starting it.

This saw reminds me of an old Husky 500 dirt bike I had years ago, the former owner raced it professionally so they had the base of the cylinder or block machined to increase compression and a ton of other mods done. The only way to start it was to tow it behind a truck and simultaneously pop the clutch and jump on the seat to get the engine to start, but once it fired, it was a monster. The thing had so much compression that even my then 280 lb weight wouldn't budge the kick-starter.
We had an old mail jeep on the farm back then and we would us it to tow the bike down the road. It would not start on dirt, and a lighter rider couldn't get enough traction to start it even in high gear.
It was fun for a while but if it died out in the woods, it wasn't much fun getting towed home or to the nearest road where someone could tow start you again.
It was fun to ride, downright scary to some but you didn't dare stall the thing if you didn't have a vehicle to tow start it with.
The guy who had it before had some sort of power starter they used at the track, that wasn't in my budget back then so we used a Jeep.

[Haleiwa]

I'm wondering if the ring is a few thousandths over.  Maybe file a few strokes off each end of the gap.

[Al_Smith]

If the rings didn't close you'd never get the piston  in the bore .If the cylinder had taper it would hang with the plug out .
On the brighter side if it was the wrong piston  this might be earth shattering because they've tried forever to soup those clam shell Stihls without much success .Tried every thing like welding the top of the pistons .Helped until the piston flew apart  .A sacrifice to the "piston Gods" perhaps< credit to Burt Munro ."worlds fastest Indian ".

[421Altered]

When you turn the saw over without the  muffler or carb on it, but with the plug installed, where does it start to get extremely hard to pull the rope in relation to the piston stroke?  And does it pull just as hard on the power stroke as it does on the compression stroke?

[yardiron]

When you turn the saw over without the  muffler or carb on it, but with the plug installed, where does it start to get extremely hard to pull the rope in relation to the piston stroke?  And does it pull just as hard on the power stroke as it does on the compression stroke?

It gets hard to turn as soon as the rings clear the ports, but only in the running direction. If I turn the thing back, it rotates past top dead center fairly easily.
I would think that at low speed, trapped air would be trapped air in either direction but there's a huge difference in pressure in either direction.
Ring gap may be something to look at because it never looses any pressure once its pushing against the compressed air in the chamber. Not ever, it holds that pressure for hours.
I've never seen a motor that wouldn't leak that pressure past the rings or somewhere if it sat at TDC for any length of time. I'm thinking maybe its a matter of the rings being just gummed up enough from sitting that it's sealed them perfectly to the piston? Or else, they got really lucky with the piston and ring fit and sealing to the cylinder walls.

When I thought more about it, the simple fact that the steel ring to cylinder wall seal being that perfect is almost impossible but I've tried locking it at TDC five times now, each time leaving it sit for several hours, (7 hours today), and each time I could hear air venting as I loosened the spark plug.
I would have thought however, that since I've soaked the combustion chamber with both Seafoam, carb cleaner, and marvel oil, that if it were any build up of old oil or fuel causing this I would have at least removed some of it. Physically looking at the piston or rings though they look new with absolutely no patter or wear showing and only minor signs of combustion atop the piston itself.
Considering this is a cheap saw, I'm not likely going to tear the motor out and break it down, I'm leaning toward just putting it together and passing it on to someone younger with stronger hands. After all, it does run very well if you can manage to pull the rope.
Another thought, if the rings were too tight, not enough end gap, then it would get better with use not worse. If the rings were too tight, it would also likely seize once it warmed up as they expanded. The super high compression doesn't seem to change with engine temperature.
I've run this saw for hours and it does fine, (I just let it run the whole time to avoid dealing with starting it).
An old timer I talked to who used to work on old two stroke bikes tells me that timing could have something to do with it? He said that on old race bikes, those with big single cylinders, if the timing was too retarded, the engine would be hard to turn over in that the combustion in the cylinder happened later forcing more air to have to be compressed than if it had already begun to burn the fuel mix a bit earlier. That makes sense to a degree but it doesn't explain two things here, one, this turns hard without any ignition applied, and no fuel. (It gets worse when there's fuel present). Two, it doesn't exhibit any signs of a motor out of time otherwise.
One thing that I can't explain is why it turns so much easier in reverse than in the direction of run. With no induced flow of air, it shouldn't affect how much air is being trapped in the combustion chamber in either direction. At speed, with vacuum present due to a retracting piston, I can understand why direction would be important but being turned slowly by hand, it should feel the same either way.
If I bring it to TDC in reverse, I can leave it at TDC without the spring effect of the compressed air, and there's minimal air being compressed, but in forward, I need to clamp the wrench I'm using to hold it at TDC. I simply can't imagine why this is the case here.
For comparison, I did the same thing with another motor I have here, an old 2 stroke string trimmer motor, and direction of rotation does no affect the compression at low speed.

I can't help but recall that many two strokes will run in either direction, (think old golf carts and such), so the fact that the compression is so much lower in reverse has me puzzled here.

[421Altered]

yardiron,  I think I can explain something, not sure, but here goes.  The reason it is easier to spin in reverse, or clockwise, is the fact that any engine has what's called piston rock.  It has to do with the way the crank throw pushes the rod, and where the piston pin is placed in the piston.  I think, out on a limb here, but, i think the rings are "digging into" the cylinder walls.  Why, I don't know.  Could be any number of reasons.  I know you said that you were not going to do much more work to it, but, if I wanted to keep a saw that's otherwise healthy, you could pull it apart, and really examine the rings, piston grooves, and measure them for spec.  Then hone the cylinder and rebuild the saw.  Or get another piston and cylinder and make sure the problem is gone.

[yardiron]

yardiron,  I think I can explain something, not sure, but here goes.  The reason it is easier to spin in reverse, or clockwise, is the fact that any engine has what's called piston rock.  It has to do with the way the crank throw pushes the rod, and where the piston pin is placed in the piston.  I think, out on a limb here, but, i think the rings are "digging into" the cylinder walls.  Why, I don't know.  Could be any number of reasons.  I know you said that you were not going to do much more work to it, but, if I wanted to keep a saw that's otherwise healthy, you could pull it apart, and really examine the rings, piston grooves, and measure them for spec.  Then hone the cylinder and rebuild the saw.  Or get another piston and cylinder and make sure the problem is gone.

I don't think that's at all what's going on here. We're talking about a motor that's likely not even fully broken in yet, let alone one with any piston rock.
There is no detectable side rock or movement the piston whatsoever. If there was an issue with piston rock I likely wouldn't have so much compression either. A piston that could rock or move also wouldn't likely be holding pressure in the combustion chamber over several hours, if not longer.
If there was any sort of out of tolerance piston rock, there would also be some other sign of wear. The cylinder has no wear pattern yet, the piston skirts look untouched, and the rings show no sign of wear at all.
I just tried something I hadn't attempted before, now that the carb and muffler are both off at the same time, I attempted to spin the motor at a slightly faster speed than just a few short pulls with the rope to test compression. With a 1" drill and a socket, I tried to spin the thing that way, all it does is unscrew the flywheel nut. So I made up a temporary washer with fingers to engage four of the fins at the same time with a set screw to prevent the nut from loosening. I made this from steel plate.
I was able to turn the motor, (with some marvel oil shot on the sides of the piston first), at 500 rpm with the compression gauge in place. I was shocked when it shot right up to 210 psi and peaked at 236 psi. By hand I barely hit the 200 mark with lots of effort and a gloved hand, but that was with the carb and exhaust on and not being able to get more than a couple of revolutions per pull by hand.

[trapper]

common on the 250 very good saw for the price but will take your arm  off starting. 

[limbwood]

i would try a different coil and see if it helps.

[sawguy21]

That is my thought too, the timing may not be retarding for starting. Have you tried it with the switch off or coil removed?

[421Altered]

What name brand of mix oil do you use, and what is the mix ratio?

[yardiron]

That is my thought too, the timing may not be retarding for starting. Have you tried it with the switch off or coil removed?

I had the coil off the saw twice to try it, it makes no difference.

[yardiron]

What name brand of mix oil do you use, and what is the mix ratio?

I've been using the Stihl HP Ultra oil I found with the saw. I've been using one 2.6 oz bottle per gallon, should be roughly 50:1.
I also have a few cans of pre-mixed fuel by VP I picked up too that are marked 40:1. I didn't figure either one would hurt it.
For my compression tests, I've been keeping the cylinder lightly oiled with Marvel oil in a small squirt can so as not to get it into the combustion chamber.
This isn't and doesn't look like a saw that's been abused, it looks like a brand new saw inside and out. Its new enough to be identical to those on the shelf at the dealer today.

[421Altered]

I am out of idea's on what may be wrong with it.  But, if it were mine, I would try changing the way I start it.   Leave the ignition switch off, pull it, then dribble some mixed gas onto the air filter, then with ignition on, give it a mighty pull.  It will still be hard to pull, but maybe less times.  The way it sounds, even one less pull would be worth it.  And as other's have said, put a Stihl ms460 rescue saw D handle on that killer.

[mrcaptainbob]

Did what most recommend to not do...used a shot of Easy-Start (ether) on the MS310. It just would NOT 'hit'. Well, it started and ran super great. Happy camper. That was last night. Took it out today and used it quite a bit. It started right up as a normal saw should. Every time!
Again, I looked at the coil air gap and set it to .006 at the coil pickup and .008 at the shoe end. (the part that appeared to be dragging the flywheel.) as for it not sparking the fuel...no idea or guess at an explanation. But...it works great now and I am very, very happy to have my go-to partner back helping me out.
Not to hyjack this post, but meant as maybe something to consider about that air gap thing....

[yardiron]

Mine is definitely not an ignition or air gap problem. It starts and runs perfect if you can manage to pull the rope and not rip out any knuckles or fingers.
I put a bicycle hanging hook in a fence post outback, I've been using that and a heavy glove to start it.
We had a lot of rain and wind over night, and a huge chunk of one of my maple trees came down in the back yard. I was out there for four hours today cutting it up, with the MS250, but I left it running as much as I could. I only shut it off for refueling and once to clear the work area a bit. It cuts great, runs strong but starting it is just painful.

A buddy stopped by after I was almost done, the saw was warm and had been running for a good half hour straight. He owns a tree business and uses saws everyday. He starts telling me I should by a pro saw, not the whimpy thing I'm using here. I shut the saw off and hand it to him. I reposition the ladder to make a few last cuts to clean up the broken stump on the tree, I ask him to start it and hand me the MS250. He grabs the saw and tries to give it a quick yank and the recoil handle slips out of his grip. He then goes for a drop start and only gets it to turn about half a rotation before letting go of the rope. He looks at me and asks if its been run out of oil or something, I said I've been using it all day, it runs fine, just start it. After a couple more tries he does the step on the handle thing and uses one of my gloves for grip and gets it going. When I was done, I shut it off and handed it down to him. He tells me I hope your done, I'm not starting that dam thing again.

He's in his early to mid thirties, and does this for a living. He's as athletic as I am fat and old and he thought its too hard to pull. I'm just glad its not me. He swears up and down someone must have done something to it to give it that much compression but I highly doubt it. Other than making a special taller piston, I can't see any other way to raise the compression that much. I think its more a matter of the rings making a 'too perfect' seal. For now I'll leave it sit, use it when I have to and maybe find something else to replace it with.

[ZeroJunk]

I apologize if I missed it and it has already been mentioned.

But, make sure the flywheel key hasn't sheared.

I had an 066 that would jerk your arm off. Turned out it had sheared the key and advanced some more than the 25 degrees before top dead center or so that is stock. I didn't use a degree wheel or anything to check it, but it was bear to get it over. Ran great if you could get it started.

[Pine Ridge]

I look forward to the weekends when i get to run my saws cutting hardwood logs, firewood, or taking out a problem tree for someone. If you dread trying to start that 025, send it down the road to a new home and get a saw that fits your needs without making you dread using it.

[upnut]

I look forward to the weekends when i get to run my saws cutting hardwood logs, firewood, or taking out a problem tree for someone. If you dread trying to start that 025, send it down the road to a new home and get a saw that fits your needs without making you dread using it.

I agree with  Pine Ridge, send it down the road. I put my HARD pulling MS250 in the yard sale pile and bought an MS241 C-M which has been a pleasure to operate. Later added an MS261 C-M which completes my saw buying for this lifetime. Unless, of course, the battery saw revolution sucks me in... :...Scott B.

[yardiron]

A sheared flywheel key would not make it hard to turn over even with a bar and socket.

I agree on sending it down the road but who would buy it like this. If a pro tree guy thinks its a bear to pull, its not likely the average guy would want it. I wouldn't get anywhere near the $300 these go for new. I'd be lucky to get $20 for it.  I'm better off just putting it on the shelf in the garage to look at rather than giving it away. At least its there if I need it that way. Even though I didn't buy it new, I still see this as a new saw since its in such perfect shape and appears to have had such little use. I'd venture to guess nearly all the cutting done with this so far has been by me. I highly doubt my 75 year old uncle used this very much with the way it pulls. (I found the receipt for the saw, he paid $329.99 plus tax for it at a local farm dealer in November of 2014). It seems they came down in price since then because the local ACE hardware near me here sells these for $299.99 new in the box with a 16" bar.

I don't need to buy anything else, I've got plenty of saws, I can always go back to my old Homelite EZ with manual oiling. Its been around since the 60's or so and still runs great.
I've also got an 036 Pro, a pair of 029 Farm Boss', an MS200T, and a dozen others that came from the same place. None of them pull as hard as this MS250.