MS 250 no start.

[Keith Lee]

Got an MS 250. Rented to a client. Returned a few hors later. Doesn't start. I check all my machines when they come back in. Check them before they go out. So, I know it was working when it went out. We offer PROPERLY pre-mixed gas (additional cost for what's used), and chain oil. The chain oil they have to buy (once they break the seal we can't take it back).
For this particular saw. I KNOW it was running just fine. A client had rented it the day before. Brought it back and was ecstatic about how it performed. I take everything with a grain of salt when people return stuff. So, as always start it. Make sure it runs. Check fluid levels, top them up. This one. I was busy working on something else, so I didn't have time to immediately look at it and check it in. I eventually get to it and it won't start. Like it doesn't have enough compression. Check the fuel and is doesn't look or smell quite right. Emptied it then filled it with good fuel. Check for spark and it good. Still won't start. Still feels like it doesn't have enough compression. Take the plug out and put my endoscope in. The cylinder looks fine on the exhaust side (one tiny score mark). Take off the muffler and peek inside. I can see some scoring. Put my endoscope in. But, this time I can actually angle it around. There's scoring all around the cylinder (as much as I can angle the endoscope). But, to me it doesn't look that bad. I've seen worse on other saws (from other makes) and they started just fine. It doesn't have the M-Tronic, so I can rule that out. Squirted some oil in the cylinder and it half starts. Does the same when I spray brake cleaner in the intake. But, won't run. I'm hoping not to have to take the thing apart and replace the cylinder and piston. Because, I have to go though our single supplier for Stihl parts. Which is frustrating as hell. The wait time is ridiculous. So, I have a few questions.
Is it possible that even light scoring can cause a no start (what I think is light scoring)? I can take pics on Tuesday. Am I missing something? I'm sure I'm not. These aren't complex machines.

 

[lone wolf]

Got an MS 250. Rented to a client. Returned a few hors later. Doesn't start. I check all my machines when they come back in. Check them before they go out. So, I know it was working when it went out. We offer PROPERLY pre-mixed gas (additional cost for what's used), and chain oil. The chain oil they have to buy (once they break the seal we can't take it back).
For this particular saw. I KNOW it was running just fine. A client had rented it the day before. Brought it back and was ecstatic about how it performed. I take everything with a grain of salt when people return stuff. So, as always start it. Make sure it runs. Check fluid levels, top them up. This one. I was busy working on something else, so I didn't have time to immediately look at it and check it in. I eventually get to it and it won't start. Like it doesn't have enough compression. Check the fuel and is doesn't look or smell quite right. Emptied it then filled it with good fuel. Check for spark and it good. Still won't start. Still feels like it doesn't have enough compression. Take the plug out and put my endoscope in. The cylinder looks fine on the exhaust side (one tiny score mark). Take off the muffler and peek inside. I can see some scoring. Put my endoscope in. But, this time I can actually angle it around. There's scoring all around the cylinder (as much as I can angle the endoscope). But, to me it doesn't look that bad. I've seen worse on other saws (from other makes) and they started just fine. It doesn't have the M-Tronic, so I can rule that out. Squirted some oil in the cylinder and it half starts. Does the same when I spray brake cleaner in the intake. But, won't run. I'm hoping not to have to take the thing apart and replace the cylinder and piston. Because, I have to go though our single supplier for Stihl parts. Which is frustrating as hell. The wait time is ridiculous. So, I have a few questions.
Is it possible that even light scoring can cause a no start (what I think is light scoring)? I can take pics on Tuesday. Am I missing something? I'm sure I'm not. These aren't complex machines.

Sure, its possible the ring can be stuck from this. They straight gassed it, probably, did you save the gas that came out for proof? If the gas that came out had oil, maybe they just beat on it with a dull chain, is the chain rocked?

 

[Keith Lee]

Sure, its possible the ring can be stuck from this. They straight gassed it, probably, did you save the gas that came out for proof? If the gas that came out had oil, maybe they just beat on it with a dull chain, is the chain rocked?

Rings actually look fine. They aren't stuck. Still expand and contract. For the gas that came out of it. I did not save it. I will in future for you guys/gals. Unfortunately, I work for a large corporate company in a rental division. So, a lowly technician calling out a client isn't an option. "Makes the company look bad...". I just get stuck with stuff that people screw up. Bring back and say it's not working/stopped working/won't start/etc... Thus is my life,

 

[ZeroJunk]

Since you said the fuel smelled funny, I had one a few weeks ago that the guy had gotten mixed up and filled the fuel tank with bar oil. I thought no big deal.
I messed with that thing and messed with it and finally figured out that the bar oil and stopped the fuel filter up.
I figured it would just mix back in with proper fuel. It did not.

If it was straight gassed when you look in the exhaust port it usually jumps out at you.

 

[stihltech]

Pull the carburetor and take it apart. Look for dirt and corrosion for starters. After that, look to see if the pulse hose or intake boot are off or leaking. Compression low? Tear it down.

 

[Hulpio]

I would measure compression. If low tear down. If ok, spark is good and carb gets fuel and impulse then swap carb with similar saw just to overrule carb issues.

 

[Oletrapper]

Got an MS 250. Rented to a client. Returned a few hors later. Doesn't start. I check all my machines when they come back in. Check them before they go out. So, I know it was working when it went out. We offer PROPERLY pre-mixed gas (additional cost for what's used), and chain oil. The chain oil they have to buy (once they break the seal we can't take it back).
For this particular saw. I KNOW it was running just fine. A client had rented it the day before. Brought it back and was ecstatic about how it performed. I take everything with a grain of salt when people return stuff. So, as always start it. Make sure it runs. Check fluid levels, top them up. This one. I was busy working on something else, so I didn't have time to immediately look at it and check it in. I eventually get to it and it won't start. Like it doesn't have enough compression. Check the fuel and is doesn't look or smell quite right. Emptied it then filled it with good fuel. Check for spark and it good. Still won't start. Still feels like it doesn't have enough compression. Take the plug out and put my endoscope in. The cylinder looks fine on the exhaust side (one tiny score mark). Take off the muffler and peek inside. I can see some scoring. Put my endoscope in. But, this time I can actually angle it around. There's scoring all around the cylinder (as much as I can angle the endoscope). But, to me it doesn't look that bad. I've seen worse on other saws (from other makes) and they started just fine. It doesn't have the M-Tronic, so I can rule that out. Squirted some oil in the cylinder and it half starts. Does the same when I spray brake cleaner in the intake. But, won't run. I'm hoping not to have to take the thing apart and replace the cylinder and piston. Because, I have to go though our single supplier for Stihl parts. Which is frustrating as hell. The wait time is ridiculous. So, I have a few questions.
Is it possible that even light scoring can cause a no start (what I think is light scoring)? I can take pics on Tuesday. Am I missing something? I'm sure I'm not. These aren't complex machines.

Good morning Keith, Send some pics. You said fuel was provided to the client. Could be that they went through what was provided and then just used straight gas as Lone Wolf suggested. Scoring of any kind can cause a no start. The pics will let all know. I personally know, and I think most will agree, that the MS 250 is one of the easiest Stihl saws to flood. A real pain in the arse. As far as putting bar oil in the fuel tank and vise versa, I think you would have immediately known that when you dumped the fuel. Stihl bar oil is as thick as molasses. I'm leaning towards bad compression because of scoring or saw is flooded. Be sure to let us know what you find. JMHO Have a great day. OT

 

[Keith Lee]

Good morning Keith, Send some pics. You said fuel was provided to the client. Could be that they went through what was provided and then just used straight gas as Lone Wolf suggested. Scoring of any kind can cause a no start. The pics will let all know. I personally know, and I think most will agree, that the MS 250 is one of the easiest Stihl saws to flood. A real pain in the arse. As far as putting bar oil in the fuel tank and vise versa, I think you would have immediately known that when you dumped the fuel. Stihl bar oil is as thick as molasses. I'm leaning towards bad compression because of scoring or saw is flooded. Be sure to let us know what you find. JMHO Have a great day. OT

No we offered to provide the pre-mixed fuel and oil. Client didn't take them. Said he had his own. So, I don't know what the heck he put in it. Unfortunately it's company policy to not accuse the client's screwing up the gear even though we know they screwed it up and I get some pretty good ones. Anyways, here are some pics. Sorry, for the poor quality. Cheap endoscope, cheap phone. But, they do what I need them to do. You should be able to see the scoring I'm taking about.

 

[sonny580]

IF any 250 dont yank your hands off when you pull the rope------ ya got MAJOR problems with it!! ---I have 3 of them here and even the oldest high hour one still pulls hard. Sounds like straight gassed to me. I was given a 251 that has the same problem!!! Gotta be straight gassed from what I can tell.

 

[Oletrapper]

No we offered to provide the pre-mixed fuel and oil. Client didn't take them. Said he had his own. So, I don't know what the heck he put in it. Unfortunately it's company policy to not accuse the client's screwing up the gear even though we know they screwed it up and I get some pretty good ones. Anyways, here are some pics. Sorry, for the poor quality. Cheap endoscope, cheap phone. But, they do what I need them to do. You should be able to see the scoring I'm taking about.View attachment 1118786View attachment 1118787View attachment 1118788

That's pretty bad. Either straight gassed or over heated because a dull chain in my opinion. Either way, new top end is in order. Thanks, OT

 

[Keith Lee]

Thanks guys for confirming what I suspected. I don't know if you read my introduction. I'm actually an auto mechanic. But, have been messing with saws, lawn mowers, mopeds, scooters, etc... since I was 7 years old (1979). They REALLY don't make them like they used to. I'd like to do a compression test. But, I lent my compression tester out years ago to a friend. Then he moved out west. I still have a bunch of his tools, he's got a bunch of mine. We just decided to call it even rather then shipping stuff across the country. I just haven't gotten around to buying a new compression tester. But, it's on my list.

 

[irhunter]

So, this is a company saw and you are fixing it while on the job. Right?

I suggest, you need to tell the boss you need a pressure/vacuum tester and a 2-stroke compression tester. Because, at this point, a compression test and a P&V test of the case and carb would be good ideas.

Based on the pics, I am not sure something else isn't causing your no-run.

But, taking the step of pulling the piston without having a P&V tester is not a great idea.

Roy

 

[SteveSr]

Thanks guys for confirming what I suspected. I don't know if you read my introduction. I'm actually an auto mechanic. But, have been messing with saws, lawn mowers, mopeds, scooters, etc... since I was 7 years old (1979). They REALLY don't make them like they used to. I'd like to do a compression test. But, I lent my compression tester out years ago to a friend. Then he moved out west. I still have a bunch of his tools, he's got a bunch of mine. We just decided to call it even rather then shipping stuff across the country. I just haven't gotten around to buying a new compression tester. But, it's on my list.

Just pull the muffler and look and post a few photos here of the rings through the exhaust port. No compression tester required.

 

[Keith Lee]

Just pull the muffler and look and post a few photos here of the rings through the exhaust port. No compression tester required.

I did post pics. You can see the scoring on the cylinder wall. There is also a scoring mark on the piston itself on the exhaust side. I think

So, this is a company saw and you are fixing it while on the job. Right?

I suggest, you need to tell the boss you need a pressure/vacuum tester and a 2-stroke compression tester. Because, at this point, a compression test and a P&V test of the case and carb would be good ideas.

Based on the pics, I am not sure something else isn't causing your no-run.

But, taking the step of pulling the piston without having a P&V tester is not a great idea.

Roy

I have my own pressure and vac tester. I need a compression tester to replace the one I lent to a friend and then he moved to the other end of the country (Canada) with. I actually have the Stihl service kit (shop tools) somewhere. But, I'm not sure where the other guys moved it to. They tend to move stuff around and not tell me. Not to mention, I don't know if it's complete. But, I'll have a look tomorrow. As I'm waiting on parts for a TON of other stuff. Supply chain issues. We only 1 supplier for Stihl stuff. It's frustrating.

 

[SteveSr]

I did post pics. You can see the scoring on the cylinder wall. There is also a scoring mark on the piston itself on the exhaust side. I think

The bore scope photos are hard to see and I don't see any of the piston and rings through the exhaust port (gold standard).

I have my own pressure and vac tester. I need a compression tester to replace the one I lent to a friend and then he moved to the other end of the country (Canada) with. I actually have the Stihl service kit (shop tools) somewhere. But, I'm not sure where the other guys moved it to. They tend to move stuff around and not tell me. Not to mention, I don't know if it's complete. But, I'll have a look tomorrow. As I'm waiting on parts for a TON of other stuff. Supply chain issues. We only 1 supplier for Stihl stuff. It's frustrating.

Compression is only relative. I have seen (and unknowingly purchased) several engines with good compression readings that ended up having scored pistons. I now pull mufflers and check the piston or my offer price goes waaaay down!