Stihl MS250 hard to pull?

[btulloh]

Don't give up on it!  It's young, has no signs of heavy use, and it's not a big saw. It's not supposed to bethat hard to pull. 

Seems like you've been through all the possible culprits, but there's something causing the problem. But what?  You just can't let a mechanical assembly defeat you!

(Easy for me to say. . .  :D )

[booman]

I had an MS880 like that.  Hurt me a few times.  A beast to start but after using it for milling for a while it actually got easier.  I know what you are talking about.  I rigged up a rope on a pulley above to start it.  It would kick back when trying to start it.

[Magicman]

I would have to pull the jug, measure the piston, and verify that it is correct for that saw.

[yardiron]

I've got a buddy with an 088 on a Logosol chainsaw mill, that saw pulls hard but its more a kickback issue then hard pull. You just have to get it up to the compression stroke and give it a good strong, quick pull. The 088 tends to kick back, the 250 is just hard to pull past TDC. The 088 may be harder to pull but the recoil has a bigger mechanical advantage over the engine compression.  

With that said, I went looking to see what other pistons would fit into a 42.5mm bore and something I noticed that made me take a second look is that all the pictures of MS250 pistons show a flat top piston?
I know I'm going only by internet pics but I don't see any dome shape at all on the pistons listed for sale that fit the 025, 230 and 250 saws.

The piston in my saw has a dome shaped top. The entire top of the piston top is convex shaped and the curve starts at the edge of the piston and is uniform across the top.
Not having another one to compare it to, I just figured that was normal. Did they use more than one style piston in these? If its not the right piston, what could it be out of?

[Al_Smith]

Interesting .I would have assumed a flat top .Factory hemi dome the only one I'm aware of is the 038 AV which also has an off set chamber .I suppose there might have been other models though .--the plot thickens ---

[ladylake]

 You can bet that domed piston is not stock and that's where all the compression is coming from.  Steve

[kenskip1]

A couple things come to mind.How long is the starting rope?If the rope is short you may loose mechanical leverage.How about the rope spool? It may have a crack in it allowing the rope to bind inside the spool causing a possible hard starting issue.Is the rope the proper diameter?To narrow a rope will allow the rope to bind inside the spool. How much did you spend for your compression tester? I would check it with other equipment.Ignition timing.If it is advanced it can be a real bear to start.All the other bases seem to have been covered. I would like to see what a Stihl dealer would say.If you have not yet done it pull the muffler and see what's inside.

[Al_Smith]

I don't know where you would find the right sized diameter piston with enough meat on it carve out a hemi domed piston .Much to many peoples dismay the raised center domed pistons by themselves cut from a stock piston do not raise the compression .On a clam shell with no easy way to lower the head deck clearance it would lower the compression .
Again nothing is impossible,somebody might have found something that would work .Problem is it works too good .

[Al_Smith]

Then comes the problem if it was a custom design hemi dome piston .How would they cut it ,CNC maybe ? I could do it because I have a radius cutter that will cut concave and convex but it would be a bear to set up .Instead of measure twice cut once it would be measure 6 dozen times with all kinds of dial indicators  etc .Take a month of Sundays for me .----geeze i think it would be easier to fly to the moon than solve this big mystery . :D   

[ZeroJunk]

It is interesting that somebody would put that effort in to a MS250.  Might have just been a case of curiosity.

Of course, those clam shells will outlast most any average saw owner if they are taken care of.

I'm of the opinion that if there was much wrong it would have flown apart already.

[Al_Smith]

I'm with you  because myself  I wouldn't put that much effort in a clam shell .They cut wood,and for all intents do a good job at it but they are not hot rods .For some unknown reason some think they can be --bless their hearts  .

[ladylake]

 https://www.youtube.com/watch?v=EHq8p-I2Fuw


 Here's a clamshell the cuts pretty good.  Steve

[yardiron]

The top of the piston doesn't look 'machined' its more of a flat gray glass beaded look. Just by looking through the plug hole and through the exhaust port, I can get a pretty good look at it.
The dome of the piston is the whole top of the piston, it starts from the sides and rises up about 1.5mm in the center above the height of the edges.
The skirt of the piston also looks different from those pictured online. The piston skirts are longer and extend about 1/4" below the pin boss.

The thing I'm having an issue with here is that I just can't imagine my uncle messing with this thing, he was well into his 70's when he bought it and he was the type of guy who didn't fix anything, he replaced it. Of course, he never got rid of anything either, it just got put on shelf or parked in the garage or barn.
I have the oem box and owners manual for the saw, it was all right next to the saw.
Of course, the recoil rope is not factory, its been changed to 3.5mm black string. (I measure 29 1/4" out of the saw with the rope pulled all the way out).

If someone messed with this , it was likely before he bought it but again, I've got the original receipt in the box for one MS250 saw, one Stihl 0000 901-4007 case, two chains, 1 gallon Stihl  0781 516 5005 bar oil, and a case of Stihl 2 stroke oil.
I have accounted for everything on the list, all still on the shelf, minus half of one bottle of 2 stroke oil.
I've run about five tanks of fuel through this thing myself so far, when I found it it had almost no signs of use.

Dumb question, I'm assuming this is an MS250 going by the emblem on the recoil cover.
There are no other decals other than safety warning labels. Could this maybe be a different model with the recoil off a 250? In other words, did any other models use the same plastic and recoil?

[Michael]

Check your PM

[Al_Smith]

Is that thing a clam shell or a removable cylinder ?Is the rear handle white or orange ?

[yardiron]

Orange handle.
The motor appears to be all one piece with only a removable bottom cap.
Just like the one's sold in the saw kits online for the MS250.

I've looked at other MS250's at the hardware store here and this sure looks like one of them.

Most have strong compression and are difficult to pull but nothing like this thing.

I put it up online for sale, I listed it for $350 or best offer, got an offer of $275, haven't answered it yet.
I listed it has having very little use but has too much compression for my old self to use, with several pics.
I'm not including the case, figuring it'll fit what ever I buy next. I'll just include what came with the saw in the original box.

I tried fitting my 029 in the case from the 250 but it won't fit, it hits the top of the saw. So this case is limited to smaller saws.
I'm wondering if an 026 would fit or do they share size with the o29?
The case is definitely limited to an 18" bar, and a saw no taller than the MS250
Its a factory steel case, all one piece, no removable scabbard like the one's they sell now. It fits the 250 like a glove.
(I can't believe the hardware store is getting $120 for just he case). When I bought my 029, in 1996, the case was only $25 extra.

[Al_Smith]

Has anybody thought of the possibility this could be a Chinese copy ?

[Pine Ridge]

Call stihl usa and give them the serial number, they can tell you what it is if its a stihl.

[Al_Smith]

I did some internet surfing on this thing .The real Stihl corporation warns about Chinese knock offs .It just seems very odd the saw in question would have a hemi domed piston .It might be interesting if the bore could be measured by using a measuring device through the exhaust port .If that measurement is not in line with the real MS 250 that would tell the tale .What would be really bad is if somebody thought they were getting the real deal only to find out it's a copy cat .If it were me I'd check it out before I sold it as the real McCoy .-----just saying --- more> 

[Al_Smith]

For several years many saw related forums have had discussions of Chinese knock offs .Most are slightly different with regards to components .Yet at the same time the internet is almost over loaded selling the things and the parts. For example they sell recoils that say for example Stihl MS 250 as a replacement part for a real one .It would only make sense a real recoil would then fit on a phony .As such it would be very easy to pull a fast one  with a phony saw and a real cover and pull the wool over somebodies  eyes who thought they were getting a good deal .Boy oh boy does that make them snort when that happens .

[yardiron]

I suppose anything is possible, but I did find a receipt for this from a Stihl dealer, along with a factory box and Stihl paperwork still in the box.

I suppose I can't swear to the fact that its the saw that came from that box but I didn't find any others there that could have either. Its the only Stihl saw in the lot other than maybe the 200T that's newer than 20 years old.
My uncle didn't use the internet, he never owned a computer.
Where is the serial number on one of these?

Going on nothing but using the back end of a digital caliper, the cylinder appears to be 42.5mm measuring across the bore through the exhaust port. Its likely not an exact measurement but it looks normal.

All of this is making me think I'm better off just selling it and forgetting about it.

[ZeroJunk]

From your prior question the 026 is a different animal.  The crankcase is split down the middle and the cylinder is a separate . Considered a professional design customarily.

I think the MS250 is the largest displacement version that runs like MS170, MS180, MS230 , or 017, 023, 025 .
Those will interchange without a lot of effort.

Not sure where a MS280 fits in with all of that. But, an 029, MS310, 039 , MS 390 are larger.

[Jack S]

Yardiron, Please dont give up now. You came to the FF and several have given good ideas and you have done an excellent job following up on all the leads very well. You are now down to just tearing it down and checking the piston and whatever else. These saws are so easy to work on less than an hour and its apart. Really  I have followed so many threads that seem to never have a outcome.  An answer or solution to this may just help others down the road someday. Please give it another round. We are all behind you on this. Wish you lived next door I'd help you   Jack

[Al_Smith]

On the clam shells,which are not my favorite  in the Stihl lineup .If it is a real Stihl it will be a good product .They don't build junk .My only experience is both the 029 and 039 which did just fine except in professional use.tree service   .My neighbor bought a used  250 from a dealer and quite frankly it did not impress me .Keeping  in mind my "fleet " is all pro models of that brand .But that said it was a very good fire wood  cutter which it was designed for .If they were all oak slayers nobody could afford them .

[kennyz]

While I was at the local Stihl dealership recently a gentleman came in looking for a saw in the 45cc range. The owner recommended the MS251 over the MS250 saying that although the 250 was a great  saw it was sometimes known to be a tough saw to pull through. He also said that Stihl was aware of this problem and never did come up with a solution for it. I don`t know how true this is, just repeating what I heard.